Bénévole : vœux d'artistes (entité Artist) et vœux de postes

Nouvelle entité `Artist` (nom + jour de passage), CRUD
`/editions/{id}/artists` (lecture ouverte à tout compte de l'édition,
écriture COORDINATION), unicité (édition, nom, date).

La fiche bénévole porte deux listes de vœux, sur le modèle de
`skill_codes` (None = inchangé, [] = vider) :
- `artist_ids` : artistes que le bénévole veut voir (`volunteer_artist`) ;
- `wished_position_ids` : postes qu'il voudrait tenir
  (`volunteer_position_wish`), distinct de l'affectation.

Un id étranger à l'édition renvoie 422 (`artist.unknown` /
`position.unknown`). Suppression d'un artiste : cascade sur les vœux.
Migration 0006. Jeu de démonstration et frontend inchangés (le front
suivra).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017uUsRg7XzopkCPWimwg9ZM

backend/tests/test_api_volunteers.py

@@ -1,10 +1,12 @@
 import datetime as dt
+import uuid
 
 from sqlmodel import select
 
 from app.models import Assignment, Availability, AvailabilityStatus, Volunteer
 from tests.factories import (
     dt_at,
+    make_artist,
     make_availability,
     make_position,
     make_shift,
@@ -56,8 +58,6 @@ def test_list_is_ordered_by_name(client, edition, session):
 
 
 def test_get_unknown_id_is_404(client, edition):
-    import uuid
-
     assert client.get(_url(edition, f"/{uuid.uuid4()}")).status_code == 404
 
 
@@ -77,6 +77,60 @@ def test_get_volunteer_of_another_edition_is_404(client, edition, session):
     assert client.get(_url(edition, f"/{stranger.id}")).status_code == 404
 
 
+def test_create_with_artist_and_position_wishes(client, edition, session):
+    artist = make_artist(session, edition)
+    position = make_position(session, edition)
+    resp = client.post(
+        _url(edition),
+        json={
+            "first_name": "Fan",
+            "last_name": "Zele",
+            "artist_ids": [str(artist.id)],
+            "wished_position_ids": [str(position.id)],
+        },
+    )
+    assert resp.status_code == 201
+    body = resp.json()
+    assert body["artist_ids"] == [str(artist.id)]
+    assert body["wished_position_ids"] == [str(position.id)]
+
+
+def test_unknown_artist_wish_is_422(client, edition):
+    resp = client.post(
+        _url(edition),
+        json={
+            "first_name": "A",
+            "last_name": "B",
+            "artist_ids": [str(uuid.uuid4())],
+        },
+    )
+    assert resp.status_code == 422
+    assert resp.json()["detail"]["code"] == "artist.unknown"
+
+
+def test_patch_replaces_and_clears_wishes(client, edition, session):
+    a1 = make_artist(session, edition, name="A1")
+    a2 = make_artist(session, edition, name="A2")
+    volunteer = make_volunteer(session, edition, email="w@ex.fr")
+
+    r1 = client.patch(
+        _url(edition, f"/{volunteer.id}"),
+        json={"artist_ids": [str(a2.id), str(a1.id), str(a2.id)]},
+    )
+    # Doublons retirés, tri par (date, nom).
+    assert r1.json()["artist_ids"] == [str(a1.id), str(a2.id)]
+
+    r2 = client.patch(
+        _url(edition, f"/{volunteer.id}"), json={"artist_ids": []}
+    )
+    assert r2.json()["artist_ids"] == []
+    # Champ absent = inchangé.
+    r3 = client.patch(
+        _url(edition, f"/{volunteer.id}"), json={"first_name": "Zoe"}
+    )
+    assert r3.json()["artist_ids"] == []
+
+
 def test_patch_replaces_skills_and_can_clear(client, edition, session):
     volunteer = make_volunteer(session, edition, email="p@ex.fr")
     r1 = client.patch(