BEP Idea: Add MongoDB query and aggregation API endpoint support.

Currently, the asset search endpoint is a basic text search feature which imposes a large computational time to be able to retrieve assets with complex search criteria.
Similarly, asset aggregations have to go through a text search and perform the actual computation on the client side.

This proposal aims to create two new endpoints:

- A MongoDB JSON query endpoint which allows a client to perform an arbitrary search on assets. Benefiting from the power of MongoDB search and indexes.

- An aggregation query which allows a client to perform aggregations on MongoDB and push the computation to the server.

These new features are implemented in a Pull Request.
BEP Upgrade proposed by Via Science Inc.
Note: Contributors agreement signed.

Review the proposal for the two requested endpoints and locate the Pull Request referenced in the issue, since the body says the features are already implemented. Verify that the API supports arbitrary MongoDB asset queries and server-side aggregations; done means both endpoint capabilities are specified and implemented.

Written by the indexing model from the issue text.