Allow NULL oauth_applications.redirect_uri in db

Generate and apply migration to remove NOT NULL constraint from `oauth_applications.redirect_uri`.

This works in conjunction with `allow_blank_redirect_uri true` in `config/initializers/doorkeeper.rb`, allowing us to save `OAuthApplications` with blank `redirect_uri` values for URI-less flows like client_credentials or password grant flows.

NOTE: Applications using `authorization_code` (or other flows that require a redirect URI) must still have a non-blank `redirect_uri`. Otherwise, `/oauth/authorize` requests with `response_type=code` will fail.

More info is available here: https://github.com/doorkeeper-gem/doorkeeper/wiki/Allow-blank-redirect-URI-for-Applications

Author: aaronskiba

db/migrate/20260219185224_allow_null_redirect_uri_in_oauth_applications.rb

@@ -0,0 +1,9 @@
+class AllowNullRedirectUriInOauthApplications < ActiveRecord::Migration[7.1]
+  def change
+    # We currently have `allow_blank_redirect_uri true` in
+    # `config/initializers/doorkeeper.rb`. Removing the NOT NULL constraint
+    # allows us to save OAuthApplications with blank redirect_uri values
+    # https://github.com/doorkeeper-gem/doorkeeper/wiki/Allow-blank-redirect-URI-for-Applications
+    change_column_null :oauth_applications, :redirect_uri, true
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.1].define(version: 2025_11_19_131055) do
+ActiveRecord::Schema[7.1].define(version: 2026_02_19_185224) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
 
@@ -280,7 +280,7 @@
     t.string "name", null: false
     t.string "uid", null: false
     t.string "secret", null: false
-    t.text "redirect_uri", null: false
+    t.text "redirect_uri"
     t.string "scopes", default: "", null: false
     t.boolean "confidential", default: true, null: false
     t.datetime "created_at", null: false