django_anysign provides generic SignerReturnView

[benoitbryon]

django_anysign.SignerReturnView is a view where signer lands back from backend page, right after he proceed/refused a signature.

Typical methods/attributes are:

• signer and get_signer => property to get signer instance from request
• signature and get_signature => property to get signature instance from request
• get_context_data() => signer in context data, signer.signature in context data
• update_signer(status, status_date) => updates signer status (backend's specific status). Not implemented.
• update_signature(status, status_date) => updates signature status (backend's specific status). Not implemented.
• template: signature/signer_return.html

[benoitbryon]

Added expectations in ticket's description.