Enhance CI pipeline and documentation

- Update Drone CI configuration to include triggers for push and tag events.
- Improve test coverage commands and add coverage checks.
- Introduce release notes generation and packaging steps in the CI pipeline.
- Add comprehensive release documentation and a checklist for the release process.
- Implement tests for GELF logging functionality.
- Update dependencies in go.mod and go.sum for better compatibility.
- Add scripts for checking coverage and generating release notes.

docs/DEFINITION_OF_DONE.md

@@ -2,11 +2,13 @@
 
 ## Purpose
 
-This Definition of Done defines the minimum quality bar for every completed change in this repository.
+This Definition of Done defines the minimum quality bar for every
+completed change in this repository.
 
 ## Mandatory Criteria
 
 1. Tests
+
 - Every code change is covered by tests where applicable.
 - New functionality includes new tests.
 - Bug fixes include at least one regression test.
@@ -14,10 +16,12 @@ This Definition of Done defines the minimum quality bar for every completed chan
 - Automated test coverage is at least 80%.
 
 1. Functional documentation
+
 - Implemented functionality is documented.
 - Public API-relevant changes are reflected in README and/or docs.
 
 1. Documentation standards
+
 - Documentation is written in English.
 - Documentation files are placed under `docs/`.
 - Exceptions: `README.md` and `AGENTS.md` remain at repository root.
@@ -25,17 +29,22 @@ This Definition of Done defines the minimum quality bar for every completed chan
 ## Technical Completion Criteria
 
 1. Build and test status
+
 - The project builds successfully.
 - Relevant test commands run successfully.
 
 1. No unresolved critical issues
+
 - No new blocking errors are introduced.
-- Known non-blocking warnings are acceptable only if unrelated to the change or documented.
+- Known non-blocking warnings are acceptable only if unrelated to the
+  change or documented.
 
 1. SonarQube status
+
 - No SonarQube errors are present.
 
 1. Documentation links and structure
+
 - Links to moved or newly added docs are valid.
 - Documentation structure remains consistent with project rules.
 
@@ -47,6 +56,7 @@ This Definition of Done defines the minimum quality bar for every completed chan
 - [ ] Automated test coverage is at least 80%.
 - [ ] Functionality is documented.
 - [ ] Documentation is in English.
-- [ ] Documentation is located under `docs/` (except `README.md` and `AGENTS.md`).
+- [ ] Documentation is located under `docs/` (except `README.md` and
+  `AGENTS.md`).
 - [ ] No SonarQube errors are present.
 - [ ] No critical regressions found.

docs/RELEASING.md

@@ -0,0 +1,115 @@
+# Releasing go-lib/gelf
+
+This document describes the process for creating a release of the
+`go-lib/gelf` library.
+
+## Overview
+
+Releases in this project are managed via Git tags. When you push a
+tag matching the pattern `v*` (for example, `v0.2.0`), the Drone
+pipeline automatically:
+
+1. Runs quality checks (tests, coverage gate, vet, vulnerability scan)
+2. Generates release notes from commits
+3. Creates a source archive (`sources.tar.gz`)
+4. Publishes a release to Gitea with attached artifacts
+
+## Versioning
+
+This library follows semantic versioning: `MAJOR.MINOR.PATCH`
+(for example, `v1.2.3`).
+
+- `v1.0.0`: breaking API changes
+- `v1.1.0`: backward-compatible features
+- `v1.0.1`: backward-compatible fixes
+
+## Prerequisites
+
+Before creating a release, ensure:
+
+1. Working tree is clean (`git status`)
+2. Tests pass locally (`go test ./...`)
+3. Coverage is at least 80%
+4. Dependencies are tidy (`go mod tidy`)
+5. Documentation is up to date (README/docs)
+
+## Create a Release
+
+### 1. Prepare (optional)
+
+Update docs, examples, or changelog if needed:
+
+```bash
+git add README.md docs/
+git commit -m "docs: prepare release"
+```
+
+### 2. Create tag
+
+```bash
+git tag -a v0.2.0 -m "Release v0.2.0"
+```
+
+### 3. Push tag
+
+```bash
+git push origin v0.2.0
+```
+
+### 4. Verify pipeline and release
+
+After pushing the tag, verify in Drone and Gitea:
+
+- Pipeline succeeded for tag build
+- Gitea release exists with artifacts:
+  - `.build/coverage.txt`
+  - `.build/sources.tar.gz`
+  - `.build/release-notes.md`
+
+## Install Released Version
+
+```bash
+# latest
+go get scm.yoorie.de/go-lib/gelf
+
+# specific
+go get scm.yoorie.de/go-lib/gelf@v0.2.0
+```
+
+## Troubleshooting
+
+### Coverage below threshold
+
+Run locally and inspect uncovered code:
+
+```bash
+go test -v -coverprofile .build/coverage.out ./...
+go tool cover -func .build/coverage.out
+```
+
+### Release step fails
+
+Common causes:
+
+- Missing Drone secret `gitea_token`
+- Tag does not match `v*`
+- Earlier pipeline step failed
+
+### Wrong tag pushed
+
+```bash
+git tag -d v0.2.0
+git push origin :refs/tags/v0.2.0
+```
+
+Then create and push the corrected tag.
+
+## Release Checklist
+
+- [ ] Tests pass locally
+- [ ] Coverage is at least 80%
+- [ ] `go vet ./...` passes
+- [ ] `govulncheck ./...` is clean or reviewed
+- [ ] Tag `vX.Y.Z` created and pushed
+- [ ] Drone pipeline succeeded
+- [ ] Gitea release contains expected artifacts