feat(rule): add flag as a built-in template variable

frontend/src/views/rules/Dns.vue

@@ -51,7 +51,7 @@
               <span slot="label">
                   Value
                   <a-tooltip
-                      title="Support template such as ${varname}">
+                      title="Support template such as ${flag}/${custom_varname}">
                     <a-icon type="question-circle-o"/>
                   </a-tooltip>
               </span>
@@ -90,7 +90,7 @@
     </a-drawer>
     <!--    rule table -->
     <a-table
-      style="overflow-x: auto;"
+        style="overflow-x: auto;"
         :columns="columns"
         :data-source="data"
         :loading="loading"

frontend/src/views/rules/Ftp.vue

@@ -42,7 +42,7 @@
                   <a-tooltip
                       title="1. The data to be returned when the client executes the download request.
                       2. Please use base64 encoding.
-                      3. Support template such as ${user}/${password}/${varname}">
+                      3. Support template such as ${user}/${password}/${flag}/${custom_varname}">
                     <a-icon type="question-circle-o"/>
                   </a-tooltip>
               </span>

frontend/src/views/rules/Http.vue

@@ -21,7 +21,7 @@
               <span slot="label">
                   Response Status Code
                   <a-tooltip
-                      title="Number between 100-600, or template such as ${query.varname}/${body.varname}/${header.varname}">
+                      title="Number between 100-600, or template such as ${query.varname}/${body.varname}/${header.varname}/${flag}/${custom_varname}">
                     <a-icon type="question-circle-o"/>
                   </a-tooltip>
               </span>