PLT-1649: add response_url support for custom slash commands (#6739)

* add response_url support for custom slash commands

* pr suggestions

* pr update / suggestion

* test fix

i18n/en.json

@@ -4783,6 +4783,34 @@
     "id": "model.job.is_valid.type.app_error",
     "translation": "Invalid job type"
   },
+  {
+    "id": "model.command_hook.id.app_error",
+    "translation": "Invalid command hook id"
+  },
+  {
+    "id": "model.command_hook.create_at.app_error",
+    "translation": "Create at must be a valid time"
+  },
+  {
+    "id": "model.command_hook.command_id.app_error",
+    "translation": "Invalid command id"
+  },
+  {
+    "id": "model.command_hook.user_id.app_error",
+    "translation": "Invalid user id"
+  },
+  {
+    "id": "model.command_hook.channel_id.app_error",
+    "translation": "Invalid channel id"
+  },
+  {
+    "id": "model.command_hook.root_id.app_error",
+    "translation": "Invalid root id"
+  },
+  {
+    "id": "model.command_hook.parent_id.app_error",
+    "translation": "Invalid parent id"
+  },
   {
     "id": "model.oauth.is_valid.app_id.app_error",
     "translation": "Invalid app id"
@@ -6503,6 +6531,26 @@
     "id": "store.sql_webhooks.update_outgoing.app_error",
     "translation": "We couldn't update the webhook"
   },
+  {
+    "id": "store.sql_command_webhooks.save.existing.app_error",
+    "translation": "You cannot update an existing CommandWebhook"
+  },
+  {
+    "id": "store.sql_command_webhooks.save.app_error",
+    "translation": "We couldn't save the CommandWebhook"
+  },
+  {
+    "id": "store.sql_command_webhooks.get.app_error",
+    "translation": "We couldn't get the webhook"
+  },
+  {
+    "id": "store.sql_command_webhooks.try_use.app_error",
+    "translation": "Unable to use the webhook"
+  },
+  {
+    "id": "store.sql_command_webhooks.try_use.invalid.app_error",
+    "translation": "Invalid webhook"
+  },
   {
     "id": "system.message.name",
     "translation": "System"
@@ -6727,6 +6775,18 @@
     "id": "web.incoming_webhook.user.app_error",
     "translation": "Couldn't find the user"
   },
+  {
+    "id": "web.command_webhook.parse.app_error",
+    "translation": "Unable to parse incoming data"
+  },
+  {
+    "id": "web.command_webhook.invalid.app_error",
+    "translation": "Invalid webhook"
+  },
+  {
+    "id": "web.command_webhook.command.app_error",
+    "translation": "Couldn't find the command"
+  },
   {
     "id": "web.init.debug",
     "translation": "Initializing web routes"