Decouple code from Bookshelf

[mkalam-alami]

The next overly ambitious technical project, and a good exercise at migrations & code refactoring.

Strategy

For each major DB entity:

1. Create a xxx.repository.ts to be used exclusively as a DAO layer
2. Migrate all Bookshelf/Knex queries from the service layer down to the repository
3. Migrate all model.save() and model.destroy() calls down to the repository
4. Make the matching TypeORM entity class implement a fromBookshelfModel() to convert a TypeORM entity to Bookshelf, be careful about how relations are mapped
5. Update the repository API to only expose entity classes instead of Bookshelf models. Migrate all impacted classes. Bookshelf-style API (.get() etc.) can be left as is for now.

This opens things up for a migration towards either TypeORM, Knex or whatever since we'll then be using plain TS classes.

Progress

(number is line count)

• [x] 32 ./entry/platform/platform.service.ts
• [ ] 32 ./event/theme/theme-stats.service.ts
• [ ] 40 ./event/manage/create/event-template.service.ts
• [ ] 64 ./event/manage/settings/event-preset.service.ts
• [ ] 104 ./entry/team/team-invite.service.ts
• [ ] 123 ./post/like/like.service.ts
• [ ] 129 ./entry/tag/tag.service.ts
• [ ] 135 ./event/dashboard/event-participation.service.ts (already uses TypeORM)
• [ ] 169 ./event/theme/theme.service.ts
• [ ] 171 ./entry/import/entry-import.service.ts
• [ ] 176 ./post/comment/comment.service.ts
• [ ] 215 ./post/post.service.ts
• [ ] 219 ./event/theme/theme-shortlist.service.ts
• [ ] 225 ./event/event.service.ts
• [ ] 225 ./event/theme/theme-voting.service.ts
• [ ] 235 ./entry/team/team.service.ts
• [ ] 259 ./user/user.service.ts (already uses TypeORM)
• [ ] 309 ./entry/highscore/highscore.service.ts
• [ ] 353 ./event/tournament/tournament.service.ts
• [ ] 389 ./entry/entry.service.ts
• [ ] 396 ./event/ratings/rating.service.ts