[EPIC] Implement Federation Filter

[perillamint]

Pitch

In case of huge relay, it is often necessary to filter out activities based on various parameters.

Such as, but not limited to

• Language
• Activity Origin

Implementation

TBD

[perillamint]

As mentioned in #12, it will impact performance a lot (adds minimum of 200ms processing delay when fetching activity from other side of the earth on every Create activity)

This ticket should be re-evaluated.

[perillamint]

This epic's scope should be reduced.

Current viable user stories:

• Push only, no receive option for mega-instances
• Server subscription (origin actor allowlist implementation)

[perillamint]

Revived epic.

It is possible to implement Hashtag or langugage based filter with the following limitation

• Only works when Relay received type: Create ActivityStream object (Not work on type: Announce object)