Refactoring - improving coverage (#371)

* Increase code coverage in acmedns

* More testing of ReadConfig() and its fallback mechanism

* Found that if someone put a '"' double quote into the filename that we configure zap to log to, it would cause the the JSON created to be invalid. I have replaced the JSON string with proper config

* Better handling of config options for api.TLS - we now error on an invalid value instead of silently failing.

added a basic test for api.setupTLS() (to increase test coverage)

* testing nameserver isOwnChallenge and isAuthoritative methods

* add a unit test for nameserver answerOwnChallenge

* fix linting errors

* bump go and golangci-lint versions in github actions

* Update golangci-lint.yml

Bumping github-actions workflow versions to accommodate some changes in upstream golanci-lint

* Bump Golang version to 1.23 (currently the oldest supported version)

Bump golanglint-ci to 2.0.2 and migrate the config file.

This should resolve the math/rand/v2 issue

* bump golanglint-ci action version

* Fixing up new golanglint-ci warnings and errors

---------

Co-authored-by: Joona Hoikkala <5235109+joohoi@users.noreply.github.com>

.github/workflows/golangci-lint.yml

@@ -8,14 +8,14 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Setup Go
-        uses: actions/setup-go@v3
+        uses: actions/setup-go@v5
         with:
-          go-version: 1.18.4
+          go-version: 1.23
 
       - name: Check out code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Run golangci-lint
-        uses: golangci/golangci-lint-action@v3
+        uses: golangci/golangci-lint-action@v7
         with:
-          version: v1.48
+          version: v2.0.2