- name: new parameter in CreateForkOption to give the forked repository (#18066)

a custom name, intended to be used when there's a name conflict
- When a fork request results in a name conflict, HTTP 409: Conflict is
  returned instead of 500
- API documentation for the above mentioned changes

Signed-off-by: realaravinth <realaravinth@batsense.net>

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: zeripath <art27@cantab.net>

modules/structs/fork.go

@@ -8,4 +8,6 @@ package structs
 type CreateForkOption struct {
 	// organization name, if forking into an organization
 	Organization *string `json:"organization"`
+	// name of the forked repository
+	Name *string `json:"name"`
 }