As shown in the tests, `KeyValuePipe.transform` can accept
`undefined`, in which case it always returns `null`.
Additionally, the typing for `string` keys can be made generic, so the
comparison function is only required to accept the relevant cases.
Finally, the typing for `number` records now shows that the comparison
function and the result entries will actually receive the string version
of the numeric keys, just as shown in the tests.
BREAKING CHANGE:
The typing of the `keyvalue` pipe has been fixed to report that for
input objects that have `number` keys, the result will contain the
string representation of the keys. This was already the case and the
code has simply been updated to reflect this. Please update the
consumers of the pipe output if they were relying on the incorrect
types. Note that this does not affect use cases where the input values
are `Map`s, so if you need to preserve `number`s, this is an effective
way.
PR Close#37447
4dfe0fa068