MM-10417 Add local image proxy and enable by default (#9967)

* MM-10417 Add local image proxy and enable by default

* Remove unused function

* Add dependencies for willnorris/imageproxy

* Fixed compilation errors

* Lock to the master version of willnorris/imageproxy

* Fix atmos/camo proxy when no SiteURL is specified

* Re-add default values for deprecated settings

* Fix unit tests added by merge

* Pass imageproxy to App struct

* Remove unneeded locking when creating the image proxy

* Remove empty test file

api4/image.go

@@ -12,12 +12,10 @@ func (api *API) InitImage() {
 }
 
 func getImage(c *Context, w http.ResponseWriter, r *http.Request) {
-	// Only redirect to our image proxy if one is enabled. Arbitrary redirects are not allowed for
-	// security reasons.
-	if transform := c.App.ImageProxyAdder(); transform != nil {
-		http.Redirect(w, r, transform(r.URL.Query().Get("url")), http.StatusFound)
+	if !*c.App.Config().ImageProxySettings.Enable {
+		http.NotFound(w, r)
 		return
 	}
 
-	http.NotFound(w, r)
+	c.App.ImageProxy.GetImage(w, r, r.URL.Query().Get("url"))
 }