refactor: markup render (#38864)

1. add missing CSP header to api & web render endpoints.
2. make jupyter render skip post-processors, nothing to process
3. make ShortLinkProcessor correctly validate URL schemes and respect
the CustomURLSchemes setting

modules/markup/common/linkify.go

@@ -8,29 +8,14 @@ package common
 
 import (
 	"bytes"
-	"regexp"
-	"sync"
 
 	"github.com/yuin/goldmark"
 	"github.com/yuin/goldmark/ast"
 	"github.com/yuin/goldmark/parser"
 	"github.com/yuin/goldmark/text"
 	"github.com/yuin/goldmark/util"
-	"mvdan.cc/xurls/v2"
 )
 
-type GlobalVarsType struct {
-	wwwURLRegexp *regexp.Regexp
-	LinkRegex    *regexp.Regexp // fast matching a URL link, no any extra validation.
-}
-
-var GlobalVars = sync.OnceValue(func() *GlobalVarsType {
-	v := &GlobalVarsType{}
-	v.wwwURLRegexp = regexp.MustCompile(`^www\.[-a-zA-Z0-9@:%._\+~#=]{2,256}\.[a-z]{2,6}((?:/|[#?])[-a-zA-Z0-9@:%_\+.~#!?&//=\(\);,'">\^{}\[\]` + "`" + `]*)?`)
-	v.LinkRegex, _ = xurls.StrictMatchingScheme("https?://")
-	return v
-})
-
 type linkifyParser struct{}
 
 var defaultLinkifyParser = &linkifyParser{}
@@ -72,7 +57,7 @@ func (s *linkifyParser) Parse(parent ast.Node, block text.Reader, pc parser.Cont
 	var protocol []byte
 	typ := ast.AutoLinkURL
 	if bytes.HasPrefix(line, protoHTTP) || bytes.HasPrefix(line, protoHTTPS) || bytes.HasPrefix(line, protoFTP) {
-		m = GlobalVars().LinkRegex.FindSubmatchIndex(line)
+		m = GlobalVars().LinkifyRegex.FindSubmatchIndex(line)
 	}
 	if m == nil && bytes.HasPrefix(line, domainWWW) {
 		m = GlobalVars().wwwURLRegexp.FindSubmatchIndex(line)