feat: refactor authentication logic and broaden test coverage (#50)

* feat: refactor authentication logic and broaden test coverage

- Improve authentication checks to only require username and token when both are provided
- Update validation logic to allow either (username and token) or remote-token for authentication
- Enhance test coverage for various authentication scenarios
- Refine error messages to indicate a generic authentication requirement instead of specifying missing username or token

Signed-off-by: appleboy <appleboy.tw@gmail.com>

* style: streamline authentication error handling in config validation

- Simplify authentication error message in config validation

Signed-off-by: appleboy <appleboy.tw@gmail.com>

---------

Signed-off-by: appleboy <appleboy.tw@gmail.com>

jenkins.go

@@ -224,7 +224,7 @@ func (jenkins *Jenkins) sendRequest(
 	req *http.Request,
 	crumb *CrumbResponse,
 ) (*http.Response, error) {
-	if jenkins.Auth != nil {
+	if jenkins.Auth != nil && jenkins.Auth.Username != "" && jenkins.Auth.Token != "" {
 		req.SetBasicAuth(jenkins.Auth.Username, jenkins.Auth.Token)
 	}
 
@@ -277,10 +277,14 @@ func (jenkins *Jenkins) postAndGetLocation(
 	path string,
 	params url.Values,
 ) (int, error) {
-	// Fetch CSRF crumb before POST request
-	crumb, err := jenkins.getCrumb(ctx)
-	if err != nil {
-		return 0, fmt.Errorf("failed to get crumb: %w", err)
+	// Fetch CSRF crumb before POST request (only if authenticated)
+	var crumb *CrumbResponse
+	if jenkins.Auth != nil && jenkins.Auth.Username != "" && jenkins.Auth.Token != "" {
+		var err error
+		crumb, err = jenkins.getCrumb(ctx)
+		if err != nil {
+			return 0, fmt.Errorf("failed to get crumb: %w", err)
+		}
 	}
 
 	requestURL := jenkins.buildURL(path, params)