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>

pkg/acmedns/testdata/test_read_fallback_config.toml

@@ -0,0 +1,36 @@
+[general]
+listen = "127.0.0.1:53"
+protocol = "both"
+domain = "test.example.org"
+nsname = "test.example.org"
+nsadmin = "test.example.org"
+records = [
+    "test.example.org. A 127.0.0.1",
+    "test.example.org. NS test.example.org.",
+]
+debug = true
+
+[database]
+engine = "dinosaur"
+connection = "roar"
+
+[api]
+ip = "0.0.0.0"
+disable_registration = false
+port = "443"
+tls = "none"
+tls_cert_privkey = "/etc/tls/example.org/privkey.pem"
+tls_cert_fullchain = "/etc/tls/example.org/fullchain.pem"
+acme_cache_dir = "api-certs"
+notification_email = ""
+corsorigins = [
+    "*"
+]
+use_header = true
+header_name = "X-is-gonna-give-it-to-ya"
+
+[logconfig]
+loglevel = "info"
+logtype = "stdout"
+logfile = "./acme-dns.log"
+logformat = "json"