Send email for invitationer, nu også med ekstra tekst

[mhewel]

No description provided.

[what-the-diff]

PR Summary

• Enhanced Email Template Handling
  This update introduces additional support for email templates in the members-related admin actions. This will allow admin users to handle email templates within the admin interface more efficiently.

• New Field Addition in Mass Invitation Form
  A new form field, named 'email_text', has been added to the 'MassInvitationForm'. This allows the selection of invitation emails when mass-inviting users.

• Email Invitation Logic Updates
  The logic for sending email invitations has been adjusted. This logic, previously part of the 'ActivityInvite.save' method, has now been relocated to a new method. This change should result in a more efficient process for managing activity invitation actions.

• Added Email Template Section in Admin Template
  A new section has been added to the 'invite_many_to_activity' admin template. This section provides details about the email template, enhancing visibility and management of email templates.

• Updated Test Case for 'email_text' Field
  The testing setup for managing the 'email_text' field in mass invite actions has been updated. This ensures the new changes remain compatible and function as expected under test conditions.

[rasmusselsmark]

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