feat: @opentelemetry/instrumentation-express instrumentation, config story

[david-luna]

express instrumentation is already included in @elastic/opentelemetry-node but a the time of writing this it has only the default options.

elastic-otel-node/packages/opentelemetry-node/lib/sdk.js

Line 54 in 7548505

new ExpressInstrumentation(),

To acknowledge the instrumentation is in place we should

• discuss if necessary to add some defaults to this configuration
• see if the current tests are enough for a sanity check
• check if necessary to have our own set of environment vars to configure it without using JS code
• start documentation and add this to the list of instrumentations

[trentm]

Now that we have getInstrumentations (https://github.com/elastic/elastic-otel-node/pull/82/files#diff-006a61fd8273284b6adc190ba00d4c2eb77d6b41b657d33d7ad480154b5f6e80R37-R40) which allows passing in config, I think we are good here. (That getInstrumentations needs docs, but that's a separate issue.)

• discuss if necessary to add some defaults to this configuration

My vote is no, at least for now. Any defaults we feel are good for users we should push upstream.

Currently available config options are here: https://github.com/open-telemetry/opentelemetry-js-contrib/blob/main/plugins/node/opentelemetry-instrumentation-express/README.md#express-instrumentation-options

[trentm]

• start documentation and add this to the list of instrumentations

I think we should leave that to #4 or other general docs issues.