Update integrations/scm_repo_link structs and urls

[brandon-welsch]

Update theses modifications to keep a functional coherence:

• Auth Service has a new updated route for integrations: /integrations -> /scm_integrations
• API has renamed a field in scm_repo_link: auth_integration_id -> auth_integration_uuid

Add a missed method for the SCMType constant:

func (t SCMType) Str() string {
	return string(t)
}

And rename all Scm... to SCM...