Implement the stream processing handler

[s-vitaliy]

Part of #144

Scope

This pull request introduces a new event-driven stream handling architecture for the streaming subsystem, focusing on improving modularity, testability, and type safety. It adds several new interfaces and types for handling streaming events, jobs, and repositories, and refactors the controller factory and handle to use these abstractions. The changes also include improvements to queue management and event processing, as well as new helper utilities for testing.

Core architecture and event handling:

• Implemented the Handler class that handles stream events.
• Added new interfaces: JobManager, StreamManager, StreamRepository, and StreamDefinition to abstract job and stream management, StreamEvent, EventType, and StreamIdentity types to standardize event handling and identity representation.

Queue and controller refactoring:

• Changed the controller factory and handle to use a strongly typed workqueue.TypedRateLimitingInterface[StreamEvent] instead of any
  Testing and utilities:

• Added a new helper in tests/helpers.go to execute a command and load a Kubernetes config, supporting flexible test environments.

• Updated generate.go to add a mockgen directive for generating mocks for the new stream interfaces, improving testability.

NOTE: tests for this code are not completed yet

Checklist

• GitHub issue exists for this change.
• Unit tests added and they pass.
• Line Coverage is at least 80%.
• Review requested on latest commit.

[github-actions]

go-test-coverage report:

  below threshold:							coverage:	threshold:
  configuration/configuration.go					 0.0% (0/18)	70%
  services/controllers/stream/handler.go				43.6% (24/55)	70%
  services/controllers/stream/stream_controller_factory.go		 0.0% (0/11)	70%
  services/controllers/stream/stream_event.go				 0.0% (0/1)	70%
  services/controllers/stream/streaming_job_controller_handle.go	 0.0% (0/26)	70%
  services/controllers/stream_class/worker.go				55.9% (38/68)	70%
  telemetry/app_metrics.go						 0.0% (0/9)	70%
  tests/mocks/stream_mocks.go						51.2% (62/121)	70%

Package coverage threshold (70%) satisfied:	FAIL
  below threshold:				coverage:	threshold:
  services/controllers/stream			26.6% (25/94)	70%
  services/controllers/stream_class		62.8% (54/86)	70%
  telemetry					 0.0% (0/9)	70%
  tests/mocks					56.9% (91/160)	70%
  configuration					 0.0% (0/18)	70%

Total coverage threshold (75%) satisfied:	FAIL
Total test coverage: 47.2% (176/373)

Files with uncovered lines:
  file:									coverage:	uncovered lines:
  configuration/configuration.go					0%		17-20 22-24 27-36 39-41 43-47 52-55 60
  services/controllers/stream/handler.go				43.6%		39-43 56-57 65-72 75-86 88 97-99 102-105 108-116 123-129 137-139
  services/controllers/stream/stream_controller_factory.go		0%		28-43 45-52 55-57
  services/controllers/stream/stream_event.go				0%		33-35
  services/controllers/stream/streaming_job_controller_handle.go	0%		30-40 42-53 55-61 63-68 71-73 75-78 81-83 85-87 89-94
  services/controllers/stream_class/handler.go				83.3%		66-72
  services/controllers/stream_class/worker.go				55.9%		44-47 60-67 73-77 89 100-103 105-108 115-131 140-142 145-147
  telemetry/app_metrics.go						0%		18-22 24 53-56 60-63 65
  tests/mocks/stream_class_mocks.go					74.4%		85-90 93-96 99-104
  tests/mocks/stream_mocks.go						51.2%		72-77 80-83 98-102 105-107 110-115 118-121 162-167 170-173 176-181 184-187 190-195 198-201 218-223 226-229 232-237 240-243 279-281 284-289 292-295 298-303 306-309

[george-zubrienko]

progress :)

[george-zubrienko]

maybe try to create a test-only plugin CRD and utilize k8s testing framework instead - if possible.

[george-zubrienko]

Suggested change

	s.logger.Error(err, "Failed to stop job for reload request", "streamId", streamEvent.StreamId().String())
	s.logger.Error(err, "Failed to stop job for backfill request", "streamId", streamEvent.StreamId().String())

[george-zubrienko]

i'd propose (not in this PR) to fire an event through event recorder that will display on the related CR - if possible