ObjectMapper managed by Spring's context

Jackson's Object Mapper in the project is not managed by Spring context, which leads to a bit of a chaos where ObjectMapper is instantiated in multiple places. It is not so much a concern of memory usage but rather lack of predictability and chaos, which can lead to subtle bugs or difficulty to explain certain behaviour.

No files or tests are named. Start by locating all ObjectMapper instantiations and the Spring configuration, then trace how each mapper is obtained and configured. Done means the project consistently uses one Spring-managed ObjectMapper and relevant behavior remains covered by the existing tests.

Written by the indexing model from the issue text.