Put a strength routine on a date

One date, one routine. On that date it is the day's session: Body Lab prescribes nothing beside it unless another session is also put on that date. Stored as a commitment, so it's withdrawn with POST /commitments/{id}/withdraw, counts toward the same limits — no more than 180 days ahead or a day back (OUT_OF_HORIZON, 400), three sessions on a date (DATE_OCCUPIED, 409), 750 standing (SCHEDULE_FULL, 409) — and a connected app is held to the same rolling quota (QUOTA_EXCEEDED, 429). Sending the same routine twice — the same date, name, duration and exercises in the same order — stores one and answers with the first one's id; a routine that differs in any of those, a corrected rep count included, is stored as a new one. Every exercise must be in the catalogue: an unknown id refuses the whole routine (UNKNOWN_EXERCISE, 422, with suggestions for each), and so does a negative weight on an exercise that can't take assistance (ASSISTANCE_NOT_POSSIBLE, 422) or a unit the exercise isn't counted in (UNIT_MISMATCH, 422). A stated weight is stored as given.