chore: Validation for purchased pricing_plan_quantity (#8809)

- Add validations based on purchased pricing_plan_quantity
- Modify the Dashboard to support the new error message

app/javascript/dashboard/routes/dashboard/settings/agents/AddAgent.vue

@@ -130,15 +130,23 @@ export default {
         this.showAlert(this.$t('AGENT_MGMT.ADD.API.SUCCESS_MESSAGE'));
         this.onClose();
       } catch (error) {
-        const { response: { data: { error: errorResponse = '' } = {} } = {} } =
-          error;
+        const {
+          response: {
+            data: {
+              error: errorResponse = '',
+              attributes: attributes = [],
+              message: attrError = '',
+            } = {},
+          } = {},
+        } = error;
+
         let errorMessage = '';
-        if (error.response.status === 422) {
+        if (error.response.status === 422 && !attributes.includes('base')) {
           errorMessage = this.$t('AGENT_MGMT.ADD.API.EXIST_MESSAGE');
         } else {
           errorMessage = this.$t('AGENT_MGMT.ADD.API.ERROR_MESSAGE');
         }
-        this.showAlert(errorResponse || errorMessage);
+        this.showAlert(errorResponse || attrError || errorMessage);
       }
     },
   },