feat(api/v2): ⭐ Implement showcases routes

[Nudelsuppe42]

[1] Feature Description
get /showcases
get /[teamId]/showcases
post /showcases
put /showcases/[showId]
del /showcases/[showId]

[SidneyNemzer]

I can take this one

[plane-sync-bte]

Synced with Plane Workspace 🔄

[WEB-12] feat(api/v2): ⭐ Implement showcases routes