feat(api): expose external_url in monitors POST and PATCH endpoints

The field was already stored in the DB, mapped through the controller,
and present on MonitorRecordTyped — but missing from CreateMonitorRequest
and UpdateMonitorRequest, so the API silently dropped it.

src/lib/types/api.ts

@@ -121,6 +121,7 @@ export interface CreateMonitorRequest {
   is_hidden?: string;
   confirmation_threshold?: number | null;
   monitor_settings_json?: MonitorSettings | null;
+  external_url?: string | null;
 }
 
 export interface CreateMonitorResponse {
@@ -141,6 +142,7 @@ export interface UpdateMonitorRequest {
   is_hidden?: string;
   confirmation_threshold?: number | null;
   monitor_settings_json?: MonitorSettings | null;
+  external_url?: string | null;
 }
 
 export interface UpdateMonitorResponse {

src/routes/(api)/api/v4/monitors/+server.ts

@@ -130,6 +130,7 @@ export const POST: RequestHandler = async ({ request }) => {
     is_hidden: body.is_hidden ?? "NO",
     confirmation_threshold: confirmationThreshold,
     monitor_settings_json: body.monitor_settings_json ? JSON.stringify(body.monitor_settings_json) : null,
+    external_url: body.external_url ?? null,
   };
 
   await db.insertMonitor(monitorData);

src/routes/(api)/api/v4/monitors/[monitor_tag]/+server.ts

@@ -79,6 +79,7 @@ export const PATCH: RequestHandler = async ({ locals, request }) => {
   updateData.monitor_type = body.monitor_type !== undefined ? body.monitor_type : existingMonitor.monitor_type;
 
   updateData.is_hidden = body.is_hidden !== undefined ? body.is_hidden : existingMonitor.is_hidden;
+  updateData.external_url = body.external_url !== undefined ? body.external_url : existingMonitor.external_url;
 
   if (body.confirmation_threshold === null) {
     // Explicit null resets the grace period to the default (1 = off); undefined keeps the existing value.

static/api-references/v4.json

@@ -1834,6 +1834,9 @@
           "monitor_settings_json": {
             "type": "object",
             "additionalProperties": true
+          },
+          "external_url": {
+            "type": "string"
           }
         },
         "additionalProperties": false
@@ -1892,6 +1895,16 @@
                 "type": "null"
               }
             ]
+          },
+          "external_url": {
+            "oneOf": [
+              {
+                "type": "string"
+              },
+              {
+                "type": "null"
+              }
+            ]
           }
         },
         "additionalProperties": false