add search functionality

[ratsclub]

Context

This introduces the search functionality previously discussed here.

What was done

• [x] Updated migrations
• [x] Added signal to update the indexing automatically
• [x] Tests (need help on where to put it)
• [x] Add the search on the API
• [x] ~Change the styling (need help on how it should look)~

Notes

One issue is that the indexing is not done automatically, hence the signals.py file. In other to index old data, you can run the following:

from django.contrib.postgres.search import SearchVector

from main.models import Post

Post.objects.update(search_post=SearchVector('title') + SearchVector('body'))

[sirodoht]

About the tests, I would say put them into main/tests/test_posts.py