Conversion trait for context types
Used to support different context types for different parts of an
application. By making each
GraphQL type only aware of as much
context as it needs to, isolation and robustness can be
improved. Implement this trait if you have contexts that can
generally be converted between each other.
The empty tuple
() can be converted into from any context type,
making it suitable for
GraphQL that don't need any context to
work, e.g. scalars or enums.