Let the bot panic if no project mapping provided

The bot cannot properly handle webhooks when no projects are configured.
So it is good to not let the bot run with such an invalid configuration.

Signed-off-by: Steven Kriegler <61625851+justusbunsi@users.noreply.github.com>

internal/settings/settings.go

@@ -107,6 +107,10 @@ func Load(configPath string) {
 		panic(fmt.Errorf("Unable to load config into struct, %v", err))
 	}
 
+	if len(fullConfig.Projects) == 0 {
+		panic("Invalid configuration. At least one project mapping is necessary.")
+	}
+
 	Gitea = fullConfig.Gitea
 	SonarQube = fullConfig.SonarQube
 	Projects = fullConfig.Projects

internal/settings/settings_test.go

@@ -155,6 +155,12 @@ sonarqube:
   url: https://example.com/sonarqube
   token:
     value: fake-sonarqube-token
+projects:
+  - sonarqube:
+      key: gitea-sonarqube-pr-bot
+    gitea:
+      owner: example-organization
+      name: pr-bot
 `))
 	os.Setenv("PRBOT_GITEA_WEBHOOK_SECRETFILE", giteaWebhookSecretFile)
 	os.Setenv("PRBOT_GITEA_TOKEN_FILE", giteaTokenFile)
@@ -219,3 +225,24 @@ func TestLoadProjectsStructure(t *testing.T) {
 
 	assert.EqualValues(t, expectedProjects, Projects)
 }
+
+func TestLoadProjectsStructureWithNoMapping(t *testing.T) {
+	invalidConfig := []byte(
+`gitea:
+  url: https://example.com/gitea
+  token:
+    value: d0fcdeb5eaa99c506831f9eb4e63fc7cc484a565
+  webhook:
+    secret: haxxor-gitea-secret
+sonarqube:
+  url: https://example.com/sonarqube
+  token:
+    value: a09eb5785b25bb2cbacf48808a677a0709f02d8e
+  webhook:
+    secret: haxxor-sonarqube-secret
+projects: []
+`)
+	WriteConfigFile(t, invalidConfig)
+
+	assert.Panics(t, func() { Load(os.TempDir()) }, "No panic for empty project mapping that is required")
+}