knotserver: add format_patch capability

appview/state/pull.go

···
 			return
 		}
 
+		if !caps.PullRequests.FormatPatch {
+			s.pages.Notice(w, "pull", "This knot doesn't support format-patch. Unfortunately, there is no fallback for now.")
+			return
+		}
+
 		// Handle the PR creation based on the type
 		if isBranchBased {
 			if !caps.PullRequests.BranchSubmissions {

knotserver/routes.go

···
 
 	capabilities := map[string]any{
 		"pull_requests": map[string]any{
+			"format_patch":       true,
 			"patch_submissions":  true,
 			"branch_submissions": true,
 			"fork_submissions":   true,

types/capabilities.go

···
 
 type Capabilities struct {
 	PullRequests struct {
+		FormatPatch       bool `json:"format_patch"`
 		PatchSubmissions  bool `json:"patch_submissions"`
 		BranchSubmissions bool `json:"branch_submissions"`
 		ForkSubmissions   bool `json:"fork_submissions"`