docs(changelog): prepare release notes for v2.1.2-frankfurt

[nanotaboada]

Summary

• Promotes [Unreleased] to [2.1.2 - Frankfurt] - 2026-04-26 (patch release, letter F)
• Updates compare links in CHANGELOG.md
• Improves /pre-release command: CodeRabbit now runs before the commit (while changes are still uncommitted); build/test/format checks are inlined directly instead of delegating to /pre-commit

What's in this release

Changed

• Field validation failures now return 422 Unprocessable Entity (RFC 4918) instead of 400 Bad Request; 400 Bad Request is reserved for malformed requests; unsupported media types return 415 Unsupported Media Type via [Consumes]; error responses follow Problem Details format (RFC 9457)

Removed

• ## How to Release section removed from CHANGELOG.md; release codenames capitalized in version headers and reference links (Normalize CHANGELOG.md structure #468)

Test plan

• CI passes
• CHANGELOG.md diff looks correct
• Merge into master, then tag v2.1.2-frankfurt

🤖 Generated with Claude Code

Summary by CodeRabbit

Release Notes

• Documentation

  • Version 2.1.2 - Frankfurt release documented with enhanced HTTP error response handling and standardized error format support.

• Chores

  • Updated pre-release workflow to include code review scanning, build verification, test execution, and code formatting checks.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 013ec0ef-51a9-4845-b995-2aa389ad660f

📥 Commits

Reviewing files that changed from the base of the PR and between e467246 and cf30a2e.

📒 Files selected for processing (1)

• .claude/commands/pre-release.md

Walkthrough

This pull request updates documentation and changelog for a release. It modifies the pre-release workflow command to replace the prior /pre-commit step with a sequence that includes optional CodeRabbit review of CHANGELOG changes, required dotnet build in Release configuration, required dotnet test, and optional code formatting checks. It also promotes the Unreleased CHANGELOG section into a new 2.1.2 - Frankfurt dated release entry with updated reference links.

Changes

Cohort / File(s)	Summary
Pre-release Workflow Documentation .claude/commands/pre-release.md	Replaced /pre-commit verification step with enhanced sequence: optional coderabbit review against CHANGELOG changes (halting only on actionable findings), required dotnet build in Release config, required dotnet test, and optional dotnet csharpier --check formatting gate. Renumbered subsequent PR proposal/opening steps accordingly.
Changelog Release Entry CHANGELOG.md	Moved "Changed" section documenting HTTP error semantics changes (validation failures from 400 to 422, 415 for unsupported media types, RFC 9457 Problem Details) from Unreleased into new 2.1.2 - Frankfurt dated release. Updated changelog compare links by advancing [unreleased] baseline to v2.1.2-frankfurt and adding corresponding [2.1.2 - Frankfurt] reference.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Possibly related PRs

• chore(claude): rename and extend slash commands #446: Modifies the same .claude/commands/pre-release.md file and adjusts pre-release workflow verification steps including CodeRabbit review integration.
• docs(changelog): prepare release notes for v2.1.1-ekaterinburg #467: Updates CHANGELOG.md by promoting Unreleased entries into a dated release section and restructuring bottom compare links using the same pattern.
• chore(claude): improve Claude Code integration #431: Adds the same verification steps (dotnet build, dotnet test, dotnet csharpier) to Claude command checklists for pre-release workflows.

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The pull request title follows Conventional Commits format with 'docs:' prefix, is descriptive and specific about preparing release notes for v2.1.2-frankfurt, and is well under the 80-character limit at 59 characters.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch release/v2.1.2-frankfurt

• 🛠️ sync documentation: Commit on current branch
• 🛠️ sync documentation: Create PR
• 🛠️ enforce http error handling: Commit on current branch
• 🛠️ enforce http error handling: Create PR
• 🛠️ idiomatic review: Commit on current branch
• 🛠️ idiomatic review: Create PR
• 🛠️ verify api contract: Commit on current branch
• 🛠️ verify api contract: Create PR

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[nanotaboada]

@coderabbitai review

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✅ Actions performed

Review triggered.

Note: CodeRabbit is an incremental review system and does not re-review already reviewed commits. This command is applicable only when automatic reviews are paused.

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In @.claude/commands/pre-release.md:
- Around line 69-90: The checklist misses an explicit commit step before
proposing the PR: insert a new step (after the "Wait for explicit approval
before committing" note and before proposing the PR) that instructs the user to
stage the changelog and commit it using the proposed commit message (the
docs(changelog): prepare release notes for vX.Y.Z-{stadium} (`#issue`) message),
then renumber the subsequent steps (move "Propose opening a PR" and "Open the
PR" down one position) so the flow is commit → propose PR → wait for approval →
open PR.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: d896684d-68a5-4d9a-891d-5b26a0594a16

📥 Commits

Reviewing files that changed from the base of the PR and between ad4b251 and e467246.

📒 Files selected for processing (2)

• .claude/commands/pre-release.md
• CHANGELOG.md

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud