Sync Mastodon IDs/profiles to local accounts

Add a new service to import some data from Mastodon accounts:

* Find users by username, store Mastodon account ID in local db when
  found
* Import display name (don't overwrite existing)
* Import avatar (don't overwrite existing)

app/services/btcpay_manager_service.rb

@@ -4,19 +4,19 @@
 class BtcpayManagerService < RestApiService
   private
 
-    def base_url
-      @base_url ||= "#{Setting.btcpay_api_url}/stores/#{Setting.btcpay_store_id}"
-    end
+  def base_url
+    @base_url ||= "#{Setting.btcpay_api_url}/stores/#{Setting.btcpay_store_id}"
+  end
 
-    def auth_token
-      @auth_token ||= Setting.btcpay_auth_token
-    end
+  def auth_token
+    @auth_token ||= Setting.btcpay_auth_token
+  end
 
-    def headers
-      {
-        "Content-Type" => "application/json",
-        "Accept" => "application/json",
-        "Authorization" => "token #{auth_token}"
-      }
-    end
+  def headers
+    {
+      "Content-Type" => "application/json",
+      "Accept" => "application/json",
+      "Authorization" => "token #{auth_token}"
+    }
+  end
 end