Support JSON logging format in operator

[ivanauth]

Summary

• Add --log-format flag to support JSON logging output
• Enable structured logging for better integration with log aggregation systems

Description

This PR adds support for JSON-formatted logs in the SpiceDB Operator, addressing issue #349. By default, the operator uses text-based logging, but operators can now use the --log-format=json flag to enable structured JSON logging.

Changes

• Added --log-format flag to the run command with validation
• Integrated zap logger for JSON output when requested
• Updated controller to accept logger as a parameter instead of creating hardcoded instances
• Added comprehensive tests for the new functionality
• Added example deployment manifest showing JSON logging configuration
• Added documentation explaining the feature and integration with log aggregation systems

Testing

• Added unit tests for log format validation
• Added integration tests verifying JSON output format
• Updated existing controller tests to pass logger parameter
• All tests pass successfully

Backward Compatibility

• Default behavior unchanged (text format)
• No breaking changes to existing deployments
• Empty log format defaults to text

Fixes #349