Make multiple endpoints more natural / intuitive #282

If a RestLink defines multiple endpoints, it's safe to assume that each of these endpoints might want different headers, credentials, field-name normalization, response transformation, and even custom fetches.

The usual answer to requests for more per-endpoint options seems to be "use the root customFetch or a responseTransformer", but these seem overly verbose workarounds for simple cases such as headers or fieldNameNormalizer, especially given how common the use-cases are.

Additionally, splitting the logic for one endpoint across multiple callbacks defined in the parent makes maintaining multiple endpoints pretty messy. I think aggregating from various REST APIs is one of GraphQL's (and thus apollo-rest-links) main selling points.

Currently, only a per-endpoint responseTransformer, as well as an undocumented per-directive fieldNameDenormalizer, are supported, and the code to achieve these 2 different exceptions seems to have been architected in different ways.

A few folks have asked for different aspects of this larger issue, and the one-off fieldNameDenormalizer exception seems to have been a response to one of those? I feel there's an opportunity to solve this holistically, allowing for the same "get from directive or endPointOptions or link default" logic when determining the final source of the following:

• responseTransformer
• fieldNameNormalizer
• fieldNameDenormalizer
• headers
• credentials
• customFetch

At the least, a per-endpoint customFetch would clean up the spread-out nature of working with multiple endpoints by allowing for cleaner exceptions / workarounds.

❤️

Related issues:

• Handling error response #150
• Bind Authorization Header With a Specific Endpoint on Every Request #174
• Allow specifying headers per endpoint #190
• Allow overriding credentials via rest directive #214
• Option to specify responseTransformer per @rest directive #215
• Allow field name normalizers/denormalizers to be specified on a per-endpoint basis #232

Issue labels

• feature