Backend fixes

Merged

• Change partner_vat to sponsor_vat !45 (merged)
• Send sponsor_vat only filled !46 (merged)
• Fix form view tests !47 (merged)
• Removed unused _check_password method in profile view
• Refactor the company data used to generate a SubscriptionRequest !48 (merged)
• Send submit form errors to OTRS !49 (merged)

WIP

• Use the user in create of service form if the partner is logged !43 (merged)

TODO

• Fix tests of submit form with OTRS notification (remove sensible data from the rq & rs)