Feature: GraphQL query interface integration and endpoint support

[kathrinrin]

Who? As a user of the vocabulary recommendation system that uses GraphQL endpoints. What? I would like to be able to use my endpoints with the vocabulary-recommendation library. Why? So that I can query vocabularies in my GraphQL endpoint.

Background

Currently the vocabulary recommendation library uses SPARQL and Elasticsearch (ES) endpoints to query datasets. GraphQL endpoints are not yet supported. In sparql.ts and elasticsearch.ts, we developed scripts that are able to communicate with an ES and SPARQL endpoint and retrieve results according to the specific ES/SPARQL query (example queries can be found here).

Goal

This feature request proposes a similar integration of GraphQL to enable retrieval of results from GraphQL endpoints. More information regarding GraphQL queries can be found here: https://graphql.org/learn/queries/.

Implementation criteria

• a pull request from a new feature branch.
• a script named graphql.ts in the /src directory in the repository.
• the aforementioned implementations are present in singleRecommendation.ts.
• in graphql.ts there is a function graphqlSuggestions that behaves similarly to elasticSuggestions and sparqlSuggestions.
• the GraphQL queries can be specified separately in the /queries directory, and a working example query is provided in this directory.
• the feature works seamlessly in the CLI tool.