Add Endpoint Workflow

Prompt file imported from jarnomaaniemi/spire-deck-builder-backend (.github/prompts/add-endpoint.prompt.md). Copyright stays with the author.

Add or modify a FastAPI endpoint in this workspace using the user request as the source of truth.

Follow project instructions:

• Workspace rules: copilot-instructions
• API file rules: api.instructions
• Test file rules: tests.instructions

Task checklist:

1. Parse the requested endpoint behavior from the prompt arguments.
2. Update app/api.py with minimal, localized edits:
   • Keep route handler names in snake_case.
   • Preserve router boundaries (public_router vs protected_router).
   • Keep protected endpoints using Security(require_api_key).
   • Preserve existing response contracts unless the request explicitly asks for a breaking change.
3. Add or update tests in tests/test_api.py:
   • Cover success path and relevant failure paths.
   • For protected routes, assert missing key (401) and invalid key (403) where applicable.
   • Keep DB isolation via DECKS_DB_PATH test DB usage.
4. Apply docs checklist:
   • If endpoint inventory changed, update endpoint summary in README.md.
   • If no doc changes are needed, state why.
5. Validate changes:
   • Always run targeted tests automatically first (pytest -k api) unless the user explicitly says not to run tests.
   • Run broader tests (pytest) when practical after targeted tests pass.
   • Report what was run and any remaining gaps.

Output format:

• Implemented: short summary of endpoint behavior and auth model.
• Files Changed: bullet list with what changed in each file.
• Test Results: commands run and pass/fail summary.
• Docs Checklist: updated/not-updated with reason.
• Follow-ups: optional next improvements if relevant.

Guardrails:

• Do not silently change unrelated endpoint behavior.
• Keep edits backward-compatible by default.
• If requirements are ambiguous, ask one concise clarification question before editing.