Add Elasticsearch

[aexvir]

Currently, our only way to search information in Zoo is to make DB queries, but with the introduction of the OpenAPI schemas support we already have a use case where we'd like to be able to search in that information without having to permanently store it in our database. There are other use cases, like files in the repository (README.md for example).

A good solution could be to use something like Elasticsearch where we could just index all the data we want to make searches over, using it as our main search backend in.