Fixed fees requiring input that has no effect

[jsugarman]

What

At least one fixed_fee requires query parameters even though they have no effect.

Why

For example, an 'Elected case not proceeded' scenario is claimed as
an advocate fee (AGFS_FEE) and requires the consumer to provide
details of scheme, fee_type_code, unit, advocate_category and offence_class.
The last two of these, however, have no impact on the "price"/amount returned.

e.g. price endpoint call for an ENP with dummy offence_class
/api/v1/fee-schemes/1/prices/?advocate_type=QC&fee_type_code=AGFS_FEE&limit_from=1&offence_class=H&scenario=12&unit=DAY

From a business perspective these are absolutely fixed fees whose value is
the same regardless of advocate involved or the offence class of the matter.

CCCD does not store offence information for its notion of a fixed fee (including
ENPs) so it does not have this data - I have worked around this by defaulting offence
to class H/band 17.1, for such instances, but this should probably not be neccesary in
the API.