Improve filter interface

There are two issues with the current filter interface (that is used by getEntries for instance):

• We need to maintain a separate query param mapping
• The return type of a filtered response is not accurate. If I call getEntries() with a filter on customersId, I'd expect the returned filter property to only have customersId.

I'd like to have an interface like this:

const response = await clockodo.getEntries({
   filter: {
      customersId: 123
   }
});

// response is now a type that looks like this

type Response = {
    paging: Paging
    filter: {
        customersId: number
    },
    entries: Array<Entry>
}

This allows us to type the filter for each endpoint. This should be doable with generics.

Start at getEntries and the filter definitions for each endpoint. Trace how filter values become query parameters and how the response type is declared. Done when endpoint filters have separate query mappings and a filtered getEntries response narrows its filter property to the supplied fields.