Ensure that entity situation id is unique.

src/lib/components/situations/SituationEdit.svelte

@@ -43,9 +43,13 @@
     const entitySituationById = {
       ...situation[entity.key_plural],
     }
-    const entitySituationId = `${entity.label ?? entity.key} ${
-      Object.keys(entitySituationById).length + 1
-    }`
+    let entitySituationId: string
+    for (let i = Object.keys(entitySituationById).length + 1; ; i++) {
+      entitySituationId = `${entity.label ?? entity.key} ${i}`
+      if (entitySituationById[entitySituationId] === undefined) {
+        break
+      }
+    }
     entitySituationById[entitySituationId] = {}
     situation = { ...situation, [entity.key_plural]: entitySituationById }