MM-61731 - enhance failed sent system bot message (#29253)

* MM-61731-enhance-failed-sent-system-bot-message

* adjust test and adjust i18n messages

* set back correct value

* improve naming and get channels logic

* hide channel name if the channel is private

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/i18n/en.json

@@ -6546,6 +6546,53 @@
     "id": "app.save_scheduled_post.save.app_error",
     "translation": "Error occurred saving the scheduled post."
   },
+  {
+    "id": "app.scheduled_post.error_reason.channel_archived",
+    "translation": "Channel is archived"
+  },
+  {
+    "id": "app.scheduled_post.error_reason.channel_not_found",
+    "translation": "Channel not found"
+  },
+  {
+    "id": "app.scheduled_post.error_reason.invalid_post",
+    "translation": "Invalid post content"
+  },
+  {
+    "id": "app.scheduled_post.error_reason.no_channel_member",
+    "translation": "Not a member of the channel"
+  },
+  {
+    "id": "app.scheduled_post.error_reason.no_channel_permission",
+    "translation": "No permission to post in channel"
+  },
+  {
+    "id": "app.scheduled_post.error_reason.thread_deleted",
+    "translation": "Thread has been deleted"
+  },
+  {
+    "id": "app.scheduled_post.error_reason.unable_to_send",
+    "translation": "Unable to send the message"
+  },
+  {
+    "id": "app.scheduled_post.error_reason.unknown",
+    "translation": "Unknown Error"
+  },
+  {
+    "id": "app.scheduled_post.error_reason.user_deleted",
+    "translation": "User account is deleted"
+  },
+  {
+    "id": "app.scheduled_post.error_reason.user_missing",
+    "translation": "User does not exist"
+  },
+  {
+    "id": "app.scheduled_post.failed_message_detail",
+    "translation": {
+      "one": "- {{.Count}} in channel {{.ChannelName}}. Reason: {{.ErrorReason}}",
+      "other": "- {{.Count}} in channel {{.ChannelName}}. Reason: {{.ErrorReason}}"
+    }
+  },
   {
     "id": "app.scheduled_post.failed_messages",
     "translation": {
@@ -6557,6 +6604,14 @@
     "id": "app.scheduled_post.permanent_delete_by_user.app_error",
     "translation": "Unable to delete scheduled posts for user."
   },
+  {
+    "id": "app.scheduled_post.private_channel",
+    "translation": "Private channel"
+  },
+  {
+    "id": "app.scheduled_post.unknown_channel",
+    "translation": "Unknown Channel"
+  },
   {
     "id": "app.scheme.delete.app_error",
     "translation": "Unable to delete this scheme."