Adding support for Sequence Coord API

[ivana-truong]

• Edited construct_query in seq_schema.py
  • Changed return value of function to JSON rather than just GraphQL string. Sequence API requires a JSON query
    for requests
  • Wrote/moved code into helper functions: _merge_query_list, _merge_query, merge_dicts, idxs_to_idx_dict,
    _idx_dict_to_name_dict, query_dict_to_graphql_string
  • Added support for field arguments. This is done by adding args as an attribute to FieldNode and checking for
    matching user input during query construction.
• Added test_seq_query.py with basic tests for each query type
• Added seq_query.py
  • Each query type (GraphQL type under Query root) is implemented as a dataclass inheriting from abstract class
    Query (similar to search api package)
  • Query args are class attributes that get passed as a dict into construct_query
• NOTE: did some quick edits and it seems like seq_schema and data_schema could be merged pretty easily

TO DO:

• The way query_dict_to_graphql_string works is a bit janky. Probably find a cleaner way. Maybe using a class that inherits from dict and overwrites some of the string representation.
• How field arguments are passed in is flawed. They are currently attributes in the query dataclasses and this would be problematic if redundantly named field args were added in the future. Other options detailed in code.