feat(metadata service): Introducing Platform Events

[jjoyce0510]

Summary
This PR introduces a new concept into the Metadata Service (GMS) of Platform Event. A Platform Event is a custom type of business (e.g. semantic) event that can be registered via the entity-registry. Platform Events are effectively platform-internal kafka events that can be emitted using the "producePlatformEvent" API of an EntityClient. When producing an event, its "name" and "payload" must be provided.

In contrast to MCP + MCL events, Platform Events do not imply any storage other than the event queue (e.g. Kafka). Platform Events are not automatically written to elastic or MySQL. Instead, it is assumed that they will be consumed from internal or external consumers of the Platform Event message stream.

Following a similar precedent to how aspects are serialized in generic fashion, Platform Events are serialized using the concept of GenericPayload inside of an envelope record called PlatformEvent, meaning that we can add and produce arbitrary platform events on a single topic (PlatformEvent_v1) without a schema registry change.

Changes

• New type of event topic in GMS: Platform Event
• Extend Entity Registry related components to support configuring, parsing, validating, and serving details about "EventSpecs"
• APIs for producing platform events
• Adding a "platform event consumer" process inside of MAE-consumer job. For now it's a no-op.
• Updating entity registry related tests to verify platform events
• Generalize GenericAspectUtils to GenericRecordUtils, since some logic is common between entity aspects and event payloads.
• Re-brand EntityEventProducer -> EventProducer to generalize.
• Re-brand EntityKafkaEventProducer -> KafkaEventProducer to generalize.

In coming PRs, we will add a few sample PlatformEvents which will more fully demonstrate their power!

Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Tests for the changes have been added/updated (if applicable)
• Docs related to the changes have been added/updated (if applicable)

[github-actions]

Unit Test Results (build & test)

  93 files  ±0    93 suites  ±0   18m 34s ⏱️ + 4m 41s
680 tests ±0  621 ✔️ ±0  59 💤 ±0  0 ❌ ±0 

Results for commit 2b0d0214. ± Comparison against base commit b843014.

♻️ This comment has been updated with latest results.

[github-actions]

Unit Test Results (metadata ingestion)

       5 files  ±0         5 suites  ±0   58m 32s ⏱️ +2s
   388 tests ±0     388 ✔️ ±0    0 💤 ±0  0 ❌ ±0 
1 787 runs  ±0  1 756 ✔️ ±0  31 💤 ±0  0 ❌ ±0 

Results for commit 2b0d0214. ± Comparison against base commit b843014.

♻️ This comment has been updated with latest results.