🚀 Enhancement: query messages by user and target

### 🔖 Enhancement description Enable querying of Messages by userId or targetId. ### 🎤 Pitch In my use-case, I would like to check if I have already scheduled a push notification for a specific user. Ideally, I would like to list all messages of status `scheduled` for the given user or target. Currently, I cannot do that as the allowed attributes for filtering are: scheduledAt, deliveredAt, deliveredTotal, status, description, providerType (according to your [docs](https://appwrite.io/docs/references/cloud/server-python/messaging#listMessages)). The current workaround is for me to keep track of the messageIds for each user, which is unnecessary duplication as AppWrite already does this for me - I just can't query it. ### 👀 Have you spent some time to check if this issue has been raised before? - [x] I checked and didn't find similar issue ### 🏢 Have you read the Code of Conduct? - [x] I have read the [Code of Conduct](https://github.com/appwrite/.github/blob/main/CODE_OF_CONDUCT.md)