v2: Project-and-CI-wide linter config (#2812)

* v2: split golangci-lint configuration into its own file to allow code editors to take advantage of it

* v2: simplify code

* v2: set the correct lint output formatting

* v2: invert the logic of linter's configuration of output formatting to allow the editor  convenience over CI-specific customization. Customize the output format in CI by passing the flag.

* v2: remove irrelevant golangci-lint config

modules/caddyhttp/server.go

@@ -169,7 +169,7 @@ func (s *Server) enforcementHandler(w http.ResponseWriter, r *http.Request, next
 		if err != nil {
 			hostname = r.Host // OK; probably lacked port
 		}
-		if strings.ToLower(r.TLS.ServerName) != strings.ToLower(hostname) {
+		if !strings.EqualFold(r.TLS.ServerName, hostname) {
 			err := fmt.Errorf("strict host matching: TLS ServerName (%s) and HTTP Host (%s) values differ",
 				r.TLS.ServerName, hostname)
 			r.Close = true