* fix nested insert with returning computed fields gives error, fix#3609
* revert using ordered hashmaps, sort columns based on ordinal postion
* fix 1. keys order 2. json/jsonb column value in nested insert returning
* add a note for sorted columns
* cast 'VALUES' expression as table row type
* use single CTE expression for generating returning for nested inserts
* allow customizing GraphQL root field names, close#981
* document v2 track_table API in reference
* support customising column field names in GraphQL schema
* [docs] add custom column fields doc in API reference
* add tests
* rename 'ColField' to 'ColumnField'
* embed column's graphql field in 'PGColumnInfo'
-> Value constructor of 'PGCol' is not exposed
-> Using 'parseJSON' to construct 'PGCol' in 'FromJSON' instances
* avoid using 'Maybe TableConfig'
* refactors & 'custom_column_fields' -> 'custom_column_names'
* cli-test: add configuration field in metadata export test
* update expected keys in `FromJSON` instance of `TableMeta`
* use `buildSchemaCacheFor` to update configuration in v2 track_table
* remove 'GraphQLName' type and use 'isValidName' exposed from parser lib
* point graphql-parser-hs library git repo to hasura
* support 'set_table_custom_fields' query API & added docs and tests
