chore(admin-clean): add docs for clean endpoint for admins

content/reference/api/admin/clean.md

@@ -0,0 +1,68 @@
+---
+title: "Clean"
+linkTitle: "Clean"
+description: >
+  Learn how to clean dangling resources as an admin in the system.
+---
+
+## Endpoint
+
+```
+PUT  /api/v1/admin/clean
+```
+
+## Filters
+
+The following optional filters are available:
+
+| Name       | Description                                                                                                | 
+| --------   | ---------------------------------------------------------------------------------------------------------- |
+| `before`   | clean resources created before a certain time (UNIX Epoch, default = "now" minus repo timeout + 5 minutes) |
+
+## Permissions
+
+COMING SOON!
+
+## Responses
+
+| Status Code | Description                                         |
+| ----------- | --------------------------------------------------- |
+| `200`       | indicates the request has succeeded                 |
+| `400`       | indicates bad request                               |
+| `401`       | indicates user does not have proper permissions     |
+| `500`       | indicates internal server issue while cleaning      |
+
+## Sample
+
+{{% alert color="warning" %}}
+This section assumes you already know how to authenticate to the API.
+
+To authenticate to the API, please review the [authentication documentation](/docs/reference/api/authentication/).
+{{% /alert %}}
+
+#### File
+
+```json
+{
+  "message": "this resource has been set to error by platform admins during maintenance"
+}
+```
+
+Note: the default value for `message` is "build cleaned by platform admin"
+
+#### Request
+
+```sh
+curl \
+  -X PUT \
+  -H "Authorization: Bearer <token>" \
+  -H "Content-Type: application/json" \
+  -d "@data.json" \
+  "http://127.0.0.1:8080/api/v1/admin/clean"
+```
+
+#### Response
+
+```json
+  "42 builds cleaned. 42 services cleaned. 42 steps cleaned."
+```