chore(blog): add release notes for 2.5.0 release

pages/blog/release-notes-2.5.0.md

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+---
+title: AsyncAPI Spec 2.5.0 Release Notes
+date: 2022-09-29T16:41:00+01:00
+type: Communication
+tags:
+  - Specification
+  - Release Notes
+cover: /img/posts/release-notes-2.5.0/cover.webp
+authors:
+  - name: Vladimír Gorej
+    photo: /img/avatars/char0n.webp
+    link: https://twitter.com/vladimirgorej
+    byline: Open Source Software Engineer, OSS contributor, author and content creator.
+excerpt: "The release of AsyncAPI 2.5 brings helpful additions, such as extended Server Variables reusability and many clarifications."
+featured: true
+---
+
+The new version of the AsyncAPI specification - 2.5.0 - is now available.
+
+> This is a minor release, and it doesn't bring any breaking changes. You can switch to it by modifying the following value in your AsyncAPI file `asyncapi: '2.4.0'` into `asyncapi: '2.5.0'`
+
+## Server Variables can be now referenced from inside the Server Object 
+
+Previous AsyncAPI 2.4.0 release came with the support of [defining Server Variable Objects as reusable components](https://www.asyncapi.com/blog/release-notes-2.4.0#server-variables-can-be-now-referenced-from-components).
+Unfortunately, AsyncAPI 2.4.0 doesn't allow referencing reusable _server variable objects_ from within the `Server Object`.
+So we ended up in a situation where reusable server variable objects can be defined but cannot be reused.
+AsyncAPI 2.5.0 remedies this deficiency by allowing the use of `Reference Object`s whenever `Server Variable Object`s can be used inside the `Server.variables` field.
+
+The following example is now fully compliant with the updated specification:
+
+```yaml
+asyncapi: 2.5.0
+servers:
+  development:
+    $ref: '#/components/servers/myserver'
+  production:
+    $ref: '#/components/servers/myserver'
+components:
+  servers:
+    myserver:
+      url: "{stage}.my-server.com:{port}"
+      protocol: ws
+      variables:
+        stage:
+          $ref: "#/components/serverVariables/stage"
+        port:
+          $ref: "#/components/serverVariables/port"
+  serverVariables:
+    stage:
+      default: dev
+    port:
+      enum: [5000, 6000]
+      default: 5000
+```
+
+This new feature was contributed by [Vladimír Gorej](https://github.com/char0n). For more detail, see [Vladimír's `/spec #776` pull request](https://github.com/asyncapi/spec/pull/776) and the [GitHub issue where Vladimír's change to `serverVariables ` was discussed](https://github.com/asyncapi/spec/issues/775).
+
+## Decorating Server Object with tags
+
+Tags categorize or group resources. 2.5.0 introduces support for defining tags at the Server level, which can be used for many use cases such as grouping servers by their features: environment name, cluster name, visibility, owner, etc.
+
+For example:
+
+```yaml
+asyncapi: '2.5.0'
+info:
+  title: Streetlights Kafka API
+  version: '1.0.0'
+servers:
+  scram-connections:
+    url: test.mykafkacluster.org:18092
+    protocol: kafka-secure
+    description: Test broker secured with scramSha256
+    security:
+      - saslScram: []
+    tags:
+      - name: "env:test-scram"
+        description: "This environment is for running internal tests through scramSha256"
+      - name: "kind:remote"
+        description: "This server is a remote server. Not exposed by the application"
+      - name: "visibility:private"
+        description: "This resource is private and only available to certain users"  
+  mtls-connections:
+    url: test.mykafkacluster.org:28092
+    protocol: kafka-secure
+    description: Test broker secured with X509
+    security:
+      - certs: []
+    tags:
+      - name: "env:test-mtls"
+        description: "This environment is for running internal tests through mTLS"
+      - name: "kind:remote"
+        description: "This server is a remote server. Not exposed by the application"
+      - name: "visibility:private"
+        description: "This resource is private and only available to certain users"
+channels: {}
+```
+
+This new feature was contributed by [Sergio Moya](https://github.com/smoya). For more detail, see [Sergio's `/spec #809` pull request](https://github.com/asyncapi/spec/pull/809) and the [GitHub issue where Sergio's change was discussed](https://github.com/asyncapi/spec/issues/654).
+
+## Added missing IBM MQ Operation Binding
+
+We noticed that we overlooked and did not define the Operation Bindings Object in the case of IBM MQ. 
+In AsyncAPI 2.5.0, the definition is empty, but its name is reserved for future use to be consistent with the rest of the bindings.
+
+This change was contributed by [Maciej Urbańczyk](https://github.com/magicmatatjahu). For more detail, see [Maciej's `/spec #840` pull request](https://github.com/asyncapi/spec/pull/840).
+
+## Added new Google Cloud Pub/Sub Bindings
+
+The specification is now extended to support another custom protocol through the bindings feature:
+
+Google Cloud Pub/Sub, thanks to [Jeremy Whitlock](https://github.com/whitlockjc). For more details, check out this [pull request](https://github.com/asyncapi/spec/pull/836) and the [binding definition](https://github.com/asyncapi/bindings/tree/master/googlepubsub).
+
+## Clarifications
+
+Here are notable clarifications that got into the AsyncAPI 2.5.0 release. Here is the list of notable clarifications that may have an impact on the tooling authors:
+
+**ChannelItem.$ref resolution rules**
+
+All references of `MUST be in the format of a URL` sentence have been substituted with `This MUST be in the form of an absolute URL`.
+The meaning of `absolute URL` is now defined by [RFC3986, section 4.3](https://datatracker.ietf.org/doc/html/rfc3986#section-4.3).
+
+**Clarification around URL resolution rules**
+
+The resolution rules around `ChannelItem.$ref` field were not clearly defined. AsyncAPI 2.5.0 comes with explicit clarification that the resolution is done as defined by the [JSON Reference](https://tools.ietf.org/html/draft-pbryan-zyp-json-ref-03).
+
+## Tooling support
+
+The following official AsyncAPI tools are already updated to support the 2.5.0 specification version:
+- JSON Schema that supports validation of AsyncAPI documents is updated in our [specification JSON schema repository](https://github.com/asyncapi/spec-json-schemas). We updated the **@asyncapi/specs** package on NPM to version `3.2`, containing the JSON Schema document for AsyncAPI Spec 2.5.0.
+- [JavaScript Parser](https://github.com/asyncapi/parser-js/) can be used to parse and validate 2.5.0 documents. Upgraded to `the 1.17.0` version.
+- [AsyncAPI React Component](https://github.com/asyncapi/asyncapi-react) allows you to render and validate the documentation of your asynchronous API provided in the AsyncAPI specification format. Upgraded to the `v1.0.0-next.43` version.
+- [HTML template](https://github.com/asyncapi/html-template) uses the latest **@asyncapi/react-component** package. Upgraded to the `0.26.0` version.
+- [JavaScript Converter](https://github.com/asyncapi/converter-js/) enables conversion from any AsyncAPI version into the 2.5.0 version of the spec. Upgraded to the `1.1.0` version.
+- [Generator](https://github.com/asyncapi/generator/) uses the latest @asyncapi/parser package, so while generating output, it can validate 2.5.0 documents. Upgraded to the `1.10.0` version.
+
+- Last but not least comes AsyncAPI Studio. [Check out AsyncAPI Studio with this YAML example](https://studio.asyncapi.com/?url=https://raw.githubusercontent.com/asyncapi/spec/v2.5.0/examples/websocket-gemini.yml).
+
+## Look ahead
+
+We aim to have a quarterly cadence of releases of the AsyncAPI specification. For more information about when to expect future releases, you can see our [release process document](https://github.com/asyncapi/spec/blob/master/RELEASE_PROCESS.md#release-cadence).
+
+We're also working on the next major release of the AsyncAPI specification: 3.0.0. If you'd like to contribute, or just follow the discussions, you can see [work on the 3.0 release issue](https://github.com/asyncapi/spec/issues/691).
+
+> Photo by <a href="https://unsplash.com/@jeremythomasphoto?utm_source=unsplash&utm_medium=referral&utm_content=creditCopyText">Jeremy Thomas</a> on <a href="https://unsplash.com/?utm_source=unsplash&utm_medium=referral&utm_content=creditCopyText">Unsplash</a>