Move all non-required fields to hidden section on Add API Backend form

[brylie]

The API Backend form currently has non-required fields showing in prominent locations (specifically documentation related fields). Show only required fields in the primary form section. Move all non-required fields to collapsing sections, which are collapsed by default.

Definition of done

• Determine the non-required fields.
• Move optional fields to collapse sections that are collapsed by default.
• Add a mark for indicating mandatory fields.