[WIP] Refactor docs

Fix #94.
Exactly. You could force a string, e.g. id, by giving `"'id'"` (extra quotes). This is different from how we do tags: `@Tag("string")` versus `@Tag(expression="id")`. I think I prefer this inconsistency over something like: `@InvalidateRoute("route", params={"type" = {"expression": "id"}})` (is this even possible?). Do you agree? I’ll update the docs to make this clearer.