Issue #2980374 by joachim, ranjith_kumar_k_u, msankhala: Add an API docs topic to cover entity characteristics in general and how they work

Issue #3309157 by dpi, larowlan: RevisionLogInterface is typehinted as always returning entity/ids, but cannot guarantee set/existing values

Issue #2665992 by alexpott, klausi, heykarthikwithu, xjm, tstoeckler: @file is not required for classes, interfaces and traits