1. `Grape::API::Instance` instead of `Grape::API` is required, unless we
solve https://gitlab.com/gitlab-org/gitlab/-/issues/215230.

2. Grape parameters defined with `Array` types (e.g. `Array[String]`,
`Array[Integer]`) must have a `coerce_with` block or they will fail to
parse properly. See
https://github.com/ruby-grape/grape/blob/master/UPGRADING.md for more
details.