docs(adr): Add ADR 0002 - CDA Authorization Filtering Integration

[vairav]

Summary

• Adds ADR 0002 documenting the Java-side authorization filtering integration
• Describes helper classes that parse x-cwms-auth-context header and generate JOOQ conditions
• Documents the integration pattern for TimeSeriesController and future controllers

Changes

• Created new ADR 0002 for CDA Authorization Filtering
• Updated RFC index to include the new document
• Documents AuthorizationContextHelper and AuthorizationFilterHelper classes
• Includes x-cwms-auth-context header format specification

Key Topics Covered

• Header parsing and user context extraction
• JOOQ condition generation for office filtering
• Embargo rules and time window constraints
• Feature flag configuration (cwms.dataapi.access.management.enabled)
• Integration patterns for controllers

Test Plan

• Verify documentation renders correctly in Sphinx
• Review code examples against actual implementation
• Confirm header format matches proxy implementation