Create graphql resolvers for pathfinder and feeder APIs #29
Description
Calls to external read APIs can be expressed in GraphQL queries via resolvers. In Hasura one can define actions that point to external APIs and these queries will be added to the schema and become available in the GUI.
For example a call to feeder.getCode can be expressed in a GraphQL query, added to our main schema so users can combine calls to the database with direct calls to the API.