Feat(integration test): MongoDB (#126)

* feat: add integration test for mongo

* style: cargo fmt

* fix: failing test

* fix: make PR requested changes

* refactor(rig-mongodb): use embeddings overhaul in integration test

* fix: error caused by container coming out of scope

* fix: failing test

* fix: rename mongodb example for uniqueness

* refactor: cleanup integration test

* fix: remove unnecessary clone

* refactor: rename FakeDefinition to Definition

* fix: add sleep

* fix: rename struct to Word