Extend the search to include comments

[molecode]

The main search functionality was already implemented. What I did was extending the existing SearchVector with some attributes from the comments and profile model:

• comments__body
• comments__user__first_name
• comments__user__last_name
• comments__user__email.

All new vectors got the weight A (because it was not specified which weight they should have). I also added a distinct() to the search query to avoid duplicates in the query result.

With this approach two new joins where introduced in the query. I did some performance measurements with an empty and with an lightly filled database and I didn't see any performance issues so far. I guess it depends how much data are in the specific tables.

This task was straight forward and I didn't need much time for it. I also added one test to the model tests.