Remove skip confirmation from trial registrations controller

What does this MR do and why?

• Remove skip confirmation
  • not used
  • see #425352 (closed) for more details
• add in override verbiage for CI checks on methods
• combine controller spec into request spec
• add test for incorrect params
• make resource building more clear in the controller by setting is explicitly and also remove ambiguity on create params around user param being required.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #425352 (closed)