Document OAuth configuration in installation.md

Configuring the OAuth client for the login using meta.sr.ht is required
when setting up a new service, but it is currently not documented.  This
patch adds a new section to the installation guide that describes the
OAuth configuration.

1 files changed, 25 insertions, 1 deletions

diff --git a/installation.md b/installation.md
index 32783d6..2448eb7 100644
--- a/installation.md
+++ b/installation.md
@@ -169,7 +169,31 @@ an example for meta.sr.ht:
         }
     }
 
-Once the proxy is configured, you should be able to log into your new service.
+Once the proxy is configured, you should be able to access your new service.
+
+# OAuth configuration
+
+For services other than meta.sr.ht, you have to create and configure an OAuth
+client before users can log into your service.  To do that, visit your profile
+on your meta.sr.ht instance, select the OAuth tab and register a new client.
+Append the path `/oauth/callback` to the URL of your service instance and
+choose this value as the base redirect URI (for example
+`https://git.sr.ht/oauth/callback`).  Update your configuration file with the
+client ID and secret.
+
+Before you can use that OAuth client, you have to set it to preauthorized using
+a database query, for example:
+
+    $ psql meta.sr.ht
+    meta.sr.ht=# select client_id, client_name from public.oauthclient;
+        client_id     | client_name
+    ------------------+-------------
+     00061df177b1e089 | git
+    (1 row)
+    meta.sr.ht=# update public.oauthclient set preauthorized = true where id = 1;
+    UPDATE 1
+
+Now you should be able to log into your new service.
 
 # Hacking on sr.ht