Prevent adding user with access key already in use (#1103)

* Release v0.10.3 (#1098)

Signed-off-by: Daniel Valdivia <18384552+dvaldivia@users.noreply.github.com>

WIP check if accesskey exists before adding user

* Added error when duplicate access key attempted

* Removed unneeded code

* Changed api to getUserInfo

* Corrected error messages

Co-authored-by: Daniel Valdivia <18384552+dvaldivia@users.noreply.github.com>

restapi/error.go

@@ -33,7 +33,8 @@ var (
 	errLicenseNotFound              = errors.New("license not found")
 	errAvoidSelfAccountDelete       = errors.New("logged in user cannot be deleted by itself")
 	errAccessDenied                 = errors.New("access denied")
-	errOauth2Provider               = errors.New("error contacting the external identity provider")
+	errOauth2Provider               = errors.New("unable to contact configured identity provider")
+	errNonUniqueAccessKey           = errors.New("access key already in use")
 )
 
 // Tiering errors