Fix missing model props

[AlexNDRmac]

Types of changes:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Small description of changes:

• Properties for sign invite that allows you to prefill text in the Signature field, allows for signers to use their saved signature, allows recipients reassign this invite to another email address, allow recipients decline the invite.
• Add support for field type stamp #149

Thanks