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/api/v1/admin/email.go

@@ -38,7 +38,7 @@ func GetAllEmails(ctx *context.APIContext) {
 	listOptions := utils.GetListOptions(ctx)
 
 	emails, maxResults, err := user_model.SearchEmails(ctx, &user_model.SearchEmailOptions{
-		Keyword:     ctx.PathParam(":email"),
+		Keyword:     ctx.PathParam("email"),
 		ListOptions: listOptions,
 	})
 	if err != nil {
@@ -82,6 +82,6 @@ func SearchEmail(ctx *context.APIContext) {
 	//   "403":
 	//     "$ref": "#/responses/forbidden"
 
-	ctx.SetPathParam(":email", ctx.FormTrim("q"))
+	ctx.SetPathParam("email", ctx.FormTrim("q"))
 	GetAllEmails(ctx)
 }