Refactor All Service Variable Names In Controllers

[Matte22]

Resolves: #1096

All controllers have been improved for clarity/readability when calling their service.

FROM:
const Asset = require(../service/${config.database.type}/AssetService);

TO:
const AssetService = require(../service/${config.database.type}/AssetService);

By renaming the variable to AssetService, it becomes evident that this is sourced from our service.