View Source ExGram.Model.WriteAccessAllowed (ex_gram v0.53.0)
This object represents a service message about a user allowing a bot to write messages after adding it to the attachment menu, launching a Web App from a link, or accepting an explicit request from a Web App sent by the method requestWriteAccess.
Check the documentation of this model in https://core.telegram.org/bots/api#writeaccessallowed