feat: add external property to coder_app (#5425)

* Add schema

* feat: add `external` property to `coder_app`

This allows exposing applications that open an external URL.

coderd/database/queries/workspaceapps.sql

@@ -21,6 +21,7 @@ INSERT INTO
         icon,
         command,
         url,
+        external,
         subdomain,
         sharing_level,
         healthcheck_url,
@@ -29,7 +30,7 @@ INSERT INTO
         health
     )
 VALUES
-    ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14) RETURNING *;
+    ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15) RETURNING *;
 
 -- name: UpdateWorkspaceAppHealthByID :exec
 UPDATE