Allow a minimum of 1 hashtag and a max of 5 hashtags per post.

[steph-koopmanschap]

Every post is forced to have a at least 1 hashtag.
So that posts without hashtag(s) can not exist.
This will improve newsfeed algorithms.

Validation should be implemented on both frontend, and backend.

The max of 5 hashtags it to prevent hashtag spam.
Also each hashtag is a minimum of 3 characters and a max of 50 characters.
< 3 character word are useless and > 50 character words are practically sentences.