Correctly implement the POST credentials method

https://docs.openstack.org/api-ref/identity/v3/index.html?expanded=authenticating-with-an-application-credential-detail,create-credential-detail#credentials
specifies that the credentials endpoint expects a credential object and returns one. This patch ensures the data is properly encoded and decoded.

src/Identity/v3/Api.php

@@ -691,6 +691,7 @@ public function postCredentials(): array
         return [
             'method' => 'POST',
             'path'   => 'credentials',
+            'jsonKey' => 'credential',
             'params' => [
                 'blob'      => $this->params->blob(),
                 'projectId' => $this->params->projectId(),
@@ -709,6 +710,15 @@ public function getCredentials(): array
         ];
     }
 
+    public function getUserCredentials(): array
+    {
+        return [
+            'method' => 'GET',
+            'path'   => 'credentials',
+            'params' => ['userId' => $this->params->userIdQueryUnderscore()],
+        ];
+    }
+
     public function getCredential(): array
     {
         return [

src/Identity/v3/Models/Credential.php

@@ -39,6 +39,8 @@ class Credential extends OperatorResource implements Creatable, Updateable, Retr
         'user_id'    => 'userId',
     ];
 
+    protected $resourceKey = 'credential';
+
     /**
      * {@inheritdoc}
      */

src/Identity/v3/Models/User.php

@@ -97,4 +97,9 @@ public function listProjects(): \Generator
     {
         return $this->model(Project::class)->enumerate($this->api->getUserProjects(), ['id' => $this->id]);
     }
+
+    public function listCredentials(): \Generator
+    {
+        return $this->model(Credential::class)->enumerate($this->api->getUserCredentials(), ['userId' => $this->id]);
+    }
 }

src/Identity/v3/Params.php

@@ -195,6 +195,15 @@ public function userIdQuery(): array
         ];
     }
 
+    public function userIdQueryUnderscore(): array
+    {
+        return [
+            'sentAs'      => 'user_id',
+            'location'    => 'query',
+            'description' => 'Filter by user ID',
+        ];
+    }
+
     public function domain(): array
     {
         return [

src/Identity/v3/Service.php

@@ -330,6 +330,16 @@ public function listCredentials(): \Generator
         return $this->model(Models\Credential::class)->enumerate($this->api->getCredentials());
     }
 
+    /**
+     * Returns a generator which will yield a collection of credential objects. The elements which generators yield can
+     * be accessed using a foreach loop. Often the API will not return the full state of the resource in collections;
+     * you will need to use retrieve() to pull in the full state of the remote resource from the API.
+     */
+    public function listUserCredentials(array $options): \Generator
+    {
+        return $this->model(Models\Credential::class)->enumerate($this->api->getUserCredentials(), $options);
+    }
+
     /**
      * Retrieves a credential object and populates its unique identifier object. This operation will not perform a GET
      * or HEAD request by default; you will need to call retrieve() if you want to pull in remote state from the API.