Rego to Elastic DSL translation performance evaluation

Implement a POC to determine if Rego to Elastic DSL translation is feasible to ensure all policies are written in Rego.

Based on outcome:

Alternative 1 (satisfactory performance): Change search to call OPA directly and perform partial evaluation and translation

Alternative 2 (unsatisfactory performance): Start supporting policy for search written in Elastic Query DSL

Related to #22 (closed).