pkg/alertmanager: add URL validation for Jira receiver (#8230)

Adds URL validation for Jira receiver configuration fields when loaded from
secrets. This ensures URLs are validated regardless of whether configurations
come from CustomResources or secrets.

pkg/alertmanager/amcfg.go

@@ -2897,6 +2897,11 @@ func (jc *jiraConfig) sanitize(amVersion semver.Version, logger *slog.Logger) er
 			}
 		}
 	}
+	if jc.APIURL != "" {
+		if _, err := validation.ValidateURL(jc.APIURL); err != nil {
+			return fmt.Errorf("invalid 'api_url': %w", err)
+		}
+	}
 
 	return jc.HTTPConfig.sanitize(amVersion, logger)
 }

pkg/alertmanager/amcfg_test.go

@@ -6069,6 +6069,24 @@ func TestSanitizeJiraConfig(t *testing.T) {
 			},
 			expectErr: true,
 		},
+		{
+			name:           "jira_configs invalid api_url returns error",
+			againstVersion: versionJiraAllowed,
+			in: &alertmanagerConfig{
+				Receivers: []*receiver{
+					{
+						JiraConfigs: []*jiraConfig{
+							{
+								APIURL:    "not-a-valid-url",
+								Project:   "Monitoring",
+								IssueType: "Bug",
+							},
+						},
+					},
+				},
+			},
+			expectErr: true,
+		},
 		{
 			name:           "jira_configs allows for supported versions",
 			againstVersion: versionJiraAllowed,