feat(tv): show cast for the entire show instead of only the last season (#778)

This uses TMDb's `aggregate_credits` instead of `credits` to get the show's cast for all seasons.

Fixes #775

server/models/common.ts

@@ -1,5 +1,6 @@
 import {
   TmdbCreditCast,
+  TmdbAggregateCreditCast,
   TmdbCreditCrew,
   TmdbExternalIds,
   TmdbVideo,
@@ -68,6 +69,18 @@ export const mapCast = (person: TmdbCreditCast): Cast => ({
   profilePath: person.profile_path,
 });
 
+export const mapAggregateCast = (person: TmdbAggregateCreditCast): Cast => ({
+  castId: person.cast_id,
+  // the first role is the one for which the actor appears the most as
+  character: person.roles[0].character,
+  creditId: person.roles[0].credit_id,
+  id: person.id,
+  name: person.name,
+  order: person.order,
+  gender: person.gender,
+  profilePath: person.profile_path,
+});
+
 export const mapCrew = (person: TmdbCreditCrew): Crew => ({
   creditId: person.credit_id,
   department: person.department,