Comment out placeholders in CAMARA_common.yaml for $ref consumption

[hdamker]

Problem description

CAMARA_common.yaml contains {{SPECIFIC_CODE}} and {{field}} placeholder patterns in Generic error responses. These are useful as documentation for API developers but make the file unparseable as a $ref target:

• YAML parsers treat placeholders as literal string values, producing invalid enum entries
• Spectral and other OpenAPI linting tools flag them
• Bundling tools that resolve $ref would propagate placeholder strings into API specs

This blocks the move toward $ref-based consumption of common schemas (#577) and the bundling model proposed in ReleaseManagement#436.

Possible evolution

Comment out the placeholder lines (~30 lines across the file) instead of deleting them:

# Before:
                  code:
                    enum:
                      - INVALID_ARGUMENT
                      - OUT_OF_RANGE
                      - "{{SPECIFIC_CODE}}"

# After:
                  code:
                    enum:
                      - INVALID_ARGUMENT
                      - OUT_OF_RANGE
                      # - "{{SPECIFIC_CODE}}"  — API-specific codes added by each API

This affects three types of placeholder occurrences:

1. Enum values — - "{{SPECIFIC_CODE}}" in code enums (5 responses)
2. Example blocks — GENERIC_4xx_{{SPECIFIC_CODE}}: example entries with their value blocks (5 responses)
3. Example message — "{{field}} is not consistent with access token." (1 occurrence in Generic403)

Benefits:

• YAML parsers, bundling tools, and Spectral ignore comments — the file becomes directly consumable via $ref
• Human readers still see the placeholder patterns as documentation
• Minimal change, no structural refactoring needed
• API-specific error code extension patterns (allOf, property override, etc.) remain a separate topic

Alternative solution

Delete the placeholder lines entirely. This also makes the file consumable but loses the documentation value for API developers who read the source file.

Additional context

• Discussion and consensus in Establish guidance for consuming schemas from CAMARA_common.yaml #577 (comment)
• Bundling design document: ReleaseManagement#436 (section 8.1)
• Validation framework umbrella: ReleaseManagement#448

Thanks and credits to @rartych for the idea and testing it in a PoC.