feat: Remove restrictions on API channel webhook_url (#2261)

db/migrate/20210513083044_remove_not_null_from_webhook_url_channel_api.rb

@@ -0,0 +1,5 @@
+class RemoveNotNullFromWebhookUrlChannelApi < ActiveRecord::Migration[6.0]
+  def change
+    change_column :channel_api, :webhook_url, :string, null: 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.define(version: 2021_04_30_100138) do
+ActiveRecord::Schema.define(version: 2021_05_13_083044) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_stat_statements"
@@ -139,7 +139,7 @@ ActiveRecord::Schema.define(version: 2021_04_30_100138) do
 
   create_table "channel_api", force: :cascade do |t|
     t.integer "account_id", null: false
-    t.string "webhook_url", null: false
+    t.string "webhook_url"
     t.datetime "created_at", precision: 6, null: false
     t.datetime "updated_at", precision: 6, null: false
   end