Builds join clauses and where conditions for joined associations.

Parses a constraint and returns a dynamic query fragment.

Extracts join fields from params and groups by association. Returns map of %{assoc_name => [{:field, field, constraint, value} | {:jsonb, field, json_key, constraint, value}, ...]}

Normalizes an in constraint value to a list: a binary is comma-split, a list passes through, anything else is wrapped.