Fix in memoriam accounts appearing in follow recommendations

[wheatear-dev]

Further to #30466, this fix prevents in memoriam accounts from appearing in accounts' follow recommendations.

This is achieved by adding an extra restriction (memorial: false) in both of the following sources of these recommendations:

• app/models/account_suggestions/source.rb
• app/models/account_suggestions/friends_of_friends_source.rb

Note - this does not invalidate any caches upon an admin "memorialising" a user. Since this action could hypothetically affect the recommendation cache for any account, and due to memorialisation being a one-off and irreversible operation, I did not see this as necessary.

[wheatear-dev]

When (or if 😅) this is merged, please preserve the notice of co-authorship by @kernal053 !

Should be as simple as leaving the commit message untouched, but I am not especially familiar with how this project uses GitHub PR's. 😌

[ClearlyClaire]

Hi! Thanks for your contribution! The change looks good to me, but could you add a couple tests in spec/models/account_suggestions for this?

(As an aside, the follow_recommendations materialized view will still store records for memorialized accounts, which is a (small) waste of resources, but this is ok because the number of trending memorialized accounts should be low. Furthermore, changing follow_recommendations is much more complex as it involves tricky database migrations)

[renchap]

(As an aside, the follow_recommendations materialized view will still store records for memorialized accounts, which is a (small) waste of resources, but this is ok because the number of trending memorialized accounts should be low.

We were discussing something similar for not ignoring "bot" accounts from recommendations, and thought about having the query return a bit more results, then filtering in Ruby to ignore the ones we dont want and limit to 30.

Not sure if this is required here as I expect memorialized accounts to be less frequent than bot accounts in trends, but this may be a solution.

[ClearlyClaire]

In this case, this is ok as far as the actual results are concerned, the filtering is done in PostgreSQL and will return the expected number of results. The potential concern is about performance, but I do not think this is a concern for memorialized accounts since there are few of it.