Adds get message endpoint

app/config/errors.php

@@ -754,5 +754,12 @@ return [
         'name' => Exception::PROVIDER_INCORRECT_TYPE,
         'description' => 'Provider with the requested ID is of incorrect type: ',
         'code' => 400,
+    ],
+
+    /** Message Errors */
+    Exception::MESSAGE_NOT_FOUND => [
+        'name' => Exception::MESSAGE_NOT_FOUND,
+        'description' => 'Message with the requested ID could not be found.',
+        'code' => 404,
     ]
 ];

app/controllers/api/messaging.php

@@ -75,7 +75,7 @@ App::get('/v1/messaging/providers/:id')
     ->label('sdk.response.code', Response::STATUS_CODE_OK)
     ->label('sdk.response.type', Response::CONTENT_TYPE_JSON)
     ->label('sdk.response.model', Response::MODEL_PROVIDER)
-    ->param('id', null, new UID(), 'Provider ID.')
+    ->param('id', '', new UID(), 'Provider ID.')
     ->inject('dbForProject')
     ->inject('response')
     ->action(function (string $id, Database $dbForProject, Response $response) {
@@ -1293,6 +1293,30 @@ App::delete('/v1/messaging/providers/:id')
         $response->noContent();
     });
 
+App::get('/v1/messaging/messages/:id')
+    ->desc('Get Message')
+    ->groups(['api', 'messaging'])
+    ->label('scope', 'messages.read')
+    ->label('sdk.auth', [APP_AUTH_TYPE_ADMIN, APP_AUTH_TYPE_KEY])
+    ->label('sdk.namespace', 'messaging')
+    ->label('sdk.method', 'getMessage')
+    ->label('sdk.description', '/docs/references/messaging/get-message.md')
+    ->label('sdk.response.code', Response::STATUS_CODE_OK)
+    ->label('sdk.response.type', Response::CONTENT_TYPE_JSON)
+    ->label('sdk.response.model', Response::MODEL_MESSAGE)
+    ->param('id', '', new UID(), 'Message ID.')
+    ->inject('dbForProject')
+    ->inject('response')
+    ->action(function (string $id, Database $dbForProject, Response $response) {
+        $message = $dbForProject->getDocument('message', $id);
+
+        if ($message->isEmpty()) {
+            throw new Exception(Exception::MESSAGE_NOT_FOUND);
+        }
+
+        $response->dynamic($message, Response::MODEL_MESSAGE);
+    });
+
 App::post('/v1/messaging/messages/email')
     ->desc('Send an email.')
     ->groups(['api', 'messaging'])

src/Appwrite/Extend/Exception.php

@@ -230,6 +230,9 @@ class Exception extends \Exception
     public const PROVIDER_ALREADY_EXISTS            = 'provider_already_exists';
     public const PROVIDER_INCORRECT_TYPE            = 'provider_incorrect_type';
 
+    /** Message */
+    public const MESSAGE_NOT_FOUND                  = 'message_not_found';
+
     protected $type = '';
     protected $errors = [];