add params to SQL ETL

[jadudm]

story

As a developer, I'd like to be able to arbitrarily parameterize SQL queries

discussion

It is possible to pass params in the body of an etl/run API call. Given a body like

{
  "key": "value"
}

it should be the case that the ExecContext call:

1. Looks for :key in the SQL, and if present
2. Binds :key to the value before making the SQL call.

This is what is already done with :date, :key_id, and :app_id. It should be done with the params as well.

acceptance