Merge-updates the vendor-editable booking configuration for one service. Every body
property is optional — absent or null properties are left unchanged, so you can send
just the fields you want to change. If nothing actually changes, the current
configuration is returned and no audit entry is written.

Rules:

• bookingWindows, when present, replaces the whole set (maximum 20 windows).
  Windows are weekly recurring preferences in local clinic time; days are full English
  day names, and each window must be long enough for the service's effective duration.
  An invalid window fails the request with 400 invalid_window naming the zero-based
  window index. There is no per-date, blackout or capacity model.
• durationMinutes and bookingLeadValue: 0 clears the value; negative values are
  rejected.
• Enum inputs (deliveryMode, bookingMode, bookingLeadUnit) are matched
  case-insensitively and stored in canonical casing; unrecognised values are rejected
  with 400 naming the valid values (nothing is silently defaulted).
• Walk-in side-effects: when the effective bookingMode is WalkIn, the service
  takes no appointments, so selfServiceBooking is forced to false and
  bookingWindows and bookingLeadValue are cleared, regardless of what else the
  request says. The audit diff records these changes.
• Setting selfServiceBooking: true while the windows list is empty is allowed, but
  members then have no windows to request — the service is effectively unbookable
  until windows are published.

Not editable via the API (ignored if sent): nationwide, locationIds and the
results-turnaround fields — service coverage is managed by the Precursor care team.
The API also cannot add or remove services; a serviceId you do not offer returns
404. Changes are recorded in your activity log with a field-by-field diff.