Add unit tests (#133)

* Add initial test & add pipeline

* Add very basic YAML config tests

* Add coverage reporting

* Add some webserver & template loading tests

* Add test cases for the helpers

* Implement initial OIDC server tests

* Test codestore & discovery checker

* Test basics of the config flow

* Add test for the HA auth provider

* Cleaned up tests & test injection

tests/mocks/scenarios/missing_token.json

@@ -0,0 +1,6 @@
+{
+    "discovery": {
+        "issuer": "https://mock-oidc-server.local",
+        "authorization_endpoint": "https://mock-oidc-server.local/authorize"
+    }
+}