init: oauth docs (#2565)

* init: oauth docs

* chore: update directories

* update: feedback

docs/install/oauth.md

@@ -0,0 +1,37 @@
+# GitHub OAuth
+
+By default, Coder is accessible via built-in authentication. Alternatively, you
+can configure Coder to enable logging in through GitHub OAuth. See below for
+configuration steps.
+
+## Step 1: Configure the OAuth application in GitHub
+
+First, [https://developer.github.com/apps/building-oauth-apps/creating-an-oauth-app/](register a GitHub OAuth app). GitHub will ask you for the following Coder parameters:
+
+- **Homepage URL**: Set to your Coder domain (e.g. `https://coder.domain.com`)
+- **User Authorization Callback URL**: Set to `https://coder.domain.com/api/v2/users/oauth2/github/callback`
+
+Note the Client ID and Client Secret generated by GitHub. You will use these
+values in the next step.
+
+## Step 2: Configure Coder with the OAuth credentials
+
+Navigate to your Coder host and run the following command to start up the Coder
+server:
+
+```console
+coder server --oauth2-github-allow-signups=true --oauth2-github-allowed-orgs="your-org" --oauth2-github-client-id="8d1...e05" --oauth2-github-client-secret="57ebc9...02c24c"
+```
+
+Alternatively, if you are running Coder as a system service, you can achieve the
+same result as the command above by adding the following environment variables
+to the `/etc/coder.d/coder.env` file:
+
+```console
+CODER_OAUTH2_GITHUB_ALLOW_SIGNUPS=true
+CODER_OAUTH2_GITHUB_ALLOWED_ORGS="your-org"
+CODER_OAUTH2_GITHUB_CLIENT_ID="8d1...e05"
+CODER_OAUTH2_GITHUB_CLIENT_SECRET="57ebc9...02c24c"
+```
+
+Once complete, run `sudo service coder restart` to reboot Coder.

docs/manifest.json

@@ -25,9 +25,14 @@
       "children": [
         {
           "title": "Postgres",
-          "description": "Learn how to create and use your own Postgres database",
-          "path": "./postgres.md"
-        }
+          "description": "Learn how to create and use your own Postgres database.",
+          "path": "./install/postgres.md"
+        },
+        {
+          "title": "GitHub OAuth",
+          "description": "Learn how to set up OAuth using your GitHub organization.",
+          "path": "./install/oauth.md"
+        } 
       ]
     },
     {