Add Cache-Control header to html and api responses, add no-transform (#20432)

`no-transform` allegedly disables CloudFlare auto-minify and we did not
set caching headers on html or api requests, which seems good to have
regardless.

Transformation is still allowed for asset requests.

Signed-off-by: Andrew Thornton <art27@cantab.net>

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

modules/context/api.go

@@ -16,6 +16,7 @@ import (
 	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/modules/cache"
 	"code.gitea.io/gitea/modules/git"
+	"code.gitea.io/gitea/modules/httpcache"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/web/middleware"
@@ -268,6 +269,7 @@ func APIContexter() func(http.Handler) http.Handler {
 				}
 			}
 
+			httpcache.AddCacheControlToHeader(ctx.Resp.Header(), 0, "no-transform")
 			ctx.Resp.Header().Set(`X-Frame-Options`, setting.CORSConfig.XFrameOptions)
 
 			ctx.Data["Context"] = &ctx