Create new create/update modals to show the form

Implementation stages

Description	MR
Setup the store to handle the form	!61697 (merged)
Create status checks form and branch selection	!61700 (merged)
Create new create/update modals to show the form	👈 You are here

What does this MR do?

With #327638 (closed) we are pivoting the status checks from being developed as part of the MR approval rules section, to its own dedicated section. This is because status checks don't "approve" an MR but rather give the MR author/merger an idea as to whether the MR passes any external processes. Putting it in a separate section helps keep the distinction that you don't need a status check to pass to merge an MR like you do approval rules.

This MR creates the create/update modals for status checks:

• Update the add and edit buttons to use the new modals
• Create modal to create new status checks which validates the data and passes it to the POST action
• Create modal to update status checks which validates the data and passes it to the PUT action

Known issues

Issue	Description	Notes
#330730	Updating a status check with a name and/or URL which is the same as a different status check returns a 412 error but doesn't return any error messages for the form to display	This is a backend issue and once this issue is resolved, the frontend will work without changes

Screenshots (strongly suggested)

Grabación_de_pantalla_2021-05-13_a_las_14.39.46

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Create
Update

Setup & testing

Note: Right now, deleting status checks is functioning within the approval rules section as per previous work. Use this area to delete the status checks for now until future MR's move the functionality to the new area

1. Enable the feature flag :ff_compliance_approval_gates
2. Go to [HOST]/gitlab-org/gitlab-test/edit and expand the Merge requests section
3. Click the status checks add button and try breaking the values in the form
4. Add a new status check
5. Check that Status checks contains the added status check
6. Click the status checks edit button and try breaking the values in the form
7. Update the status check
8. Check that Status checks contains the updated status check

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because this is behind the :ff_compliance_approval_gates feature flag.
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team

Related to #327638 (closed)