[FIX] Activity view performance

Implements [ticket 2759](https://www.openproject.org/work_packages/2759)

:exclamation: is related to openproject-costs [PR 69](https://github.com/finnlabs/openproject-costs/pull/69)
:exclamation: is related to openproject-meeting [PR 31](https://github.com/finnlabs/openproject-meeting/pull/31)
:exclamation: is related to openproject-terms [PR 11](https://github.com/finnlabs/openproject-terms/pull/11)