fix: updating with minor fixes and support for custom types

[nnshah1]

What does the PR do?

• Added test for iterator mode of subscription

• Added default for event topic and event type

• Added support for automatic serialization of typed that aren't bytes (using json)

• Added support for retrieving payload as a type - json by default

Checklist

• PR title reflects the change and is of format <commit_type>: <Title>
• [x ] Changes are described in the pull request.
• Related issues are referenced.
• Populated github labels field
• Added test plan and verified test passes.
• Verified that the PR passes existing CI.
• Verified copyright is correct on all changed files.
• Added succinct git squash message before merging ref.
• All template sections are filled out.
• Optional: Additional screenshots for behavior/output changes with before/after.

Commit Type:

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• build
• ci
• docs
• feat
• fix
• perf
• refactor
• revert
• style
• test

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Test plan:

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Background

Related Issues: (use one of the action keywords Closes / Fixes / Resolves / Relates to)

• closes GitHub issue: #xxx