Compile and render Synapse's docs into a browsable, mobile-friendly and searchable website (#10086)

docs/usage/administration/admin_api/README.md

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+# The Admin API
+
+## Authenticate as a server admin
+
+Many of the API calls in the admin api will require an `access_token` for a
+server admin. (Note that a server admin is distinct from a room admin.)
+
+A user can be marked as a server admin by updating the database directly, e.g.:
+
+```sql
+UPDATE users SET admin = 1 WHERE name = '@foo:bar.com';
+```
+
+A new server admin user can also be created using the `register_new_matrix_user`
+command. This is a script that is located in the `scripts/` directory, or possibly
+already on your `$PATH` depending on how Synapse was installed.
+
+Finding your user's `access_token` is client-dependent, but will usually be shown in the client's settings.
+
+## Making an Admin API request
+Once you have your `access_token`, you will need to authenticate each request to an Admin API endpoint by
+providing the token as either a query parameter or a request header. To add it as a request header in cURL:
+
+```sh
+curl --header "Authorization: Bearer <access_token>" <the_rest_of_your_API_request>
+```
+
+For more details on access tokens in Matrix, please refer to the complete
+[matrix spec documentation](https://matrix.org/docs/spec/client_server/r0.6.1#using-access-tokens).