Clarify path param naming (#32969)

In history (from some legacy frameworks), both `:name` and `name` are
supported as path path name, `:name` is an alias to `name`.

To make code consistent, now we should only use `name` but not `:name`.

Also added panic check in related functions to make sure the name won't
be abused in case some downstreams still use them.

routers/web/repo/attachment.go

@@ -154,5 +154,5 @@ func ServeAttachment(ctx *context.Context, uuid string) {
 
 // GetAttachment serve attachments
 func GetAttachment(ctx *context.Context) {
-	ServeAttachment(ctx, ctx.PathParam(":uuid"))
+	ServeAttachment(ctx, ctx.PathParam("uuid"))
 }