fix: allow empty appName as it may come in the url (#3953)

## About the changes
Edit application under
https://app.unleash-hosted.com/demo/applications/test-app is currently
not working as the appName is expected to come in the request body, but
it's actually part of the url. We have two options here:
1. We change the UI to adapt to the expectations of the request by
adding appName to the request body (and eventually removing appName from
the URL, which would be a breaking change)
2. We remove the restriction of only sending the appName in the body and
take the one that comes in the URL. We have a validation that verifies
that at least one of the two sets the appName
([here](e376088668/src/lib/services/client-metrics/instance-service.ts (L208))
we validate using [this
schema](e376088668/src/lib/services/client-metrics/schema.ts (L55-L70)))

In terms of REST API, we can assume that the appName will be present in
the resource `/api/admin/metrics/applications` (an endpoint we don't
have), but when we're updating an application we should refer to that
application by its URL: `/api/admin/metrics/applications/<appName>` and
the presence of an appName in the body might indicate that we're trying
to change the name of the application (something we currently not
support)

Based on the above, I believe going with the second option is best, as
it adheres to REST principles and does not require a breaking change.
Despite that, we only support updating applications as the creation is
done from metrics ingestion

Fixes: #3580

src/lib/openapi/spec/create-application-schema.ts

@@ -5,7 +5,6 @@ export const createApplicationSchema = {
     type: 'object',
     additionalProperties: true,
     description: 'Reported application information from Unleash SDKs',
-    required: ['appName'],
     properties: {
         appName: {
             description: 'Name of the application',

src/lib/routes/admin-api/metrics.test.ts

@@ -84,6 +84,20 @@ test('should store application', () => {
         .expect(202);
 });
 
+test('should store application coming from edit application form', () => {
+    expect.assertions(0);
+    const appName = '123!23';
+
+    return request
+        .post(`/api/admin/metrics/applications/${appName}`)
+        .send({
+            url: 'http://test.com',
+            description: 'This is an optional description',
+            icon: 'arrow-down',
+        })
+        .expect(202);
+});
+
 test('should store application details without strategies', () => {
     expect.assertions(0);
     const appName = '123!23';

src/test/e2e/api/openapi/__snapshots__/openapi.e2e.test.ts.snap

@@ -1576,9 +1576,6 @@ The provider you choose for your addon dictates what properties the \`parameters
             "type": "string",
           },
         },
-        "required": [
-          "appName",
-        ],
         "type": "object",
       },
       "createFeatureSchema": {