Support for dynamic headers on GraphQL clients

[jmartisk]

Preparation for OIDC client integration (quarkusio/quarkus#35878)
Quarkus-side part of the integration: https://github.com/jmartisk/quarkus/tree/oidc-token

[sberyozkin]

I'm not a GraphQL expert, but the update to the typesafe client to support dynamic headers looks sound and hopefully will be of use not only for OIDC client integrations, LGTM

[t1]

Sorry for taking so long to take a look. This adds a dependency on Vert.x to the Typesafe Client APIs. I understand that the mvn dependency had been introduced for the dynamic client, but if we try to promote the Typesafe Client APIs to MP, we would have to break the API.

And there are not tests 😢

[jmartisk]

Sorry for taking so long to take a look. This adds a dependency on Vert.x to the Typesafe Client APIs. I understand that the mvn dependency had been introduced for the dynamic client, but if we try to promote the Typesafe Client APIs to MP, we would have to break the API.

There's no Vert.x dependency, you probably mean Mutiny. However, you may be right that perhaps we can keep it only in the vertx-implementation of the builder and move it out of the general builder... Actually, turns out I accidentally added the dynamicHeader method to the TypesafeGraphQLClientBuilder but not DynamicGraphQLClientBuilder, so I'll remove it. Good point.

And there are not tests 😢

Tests with an actual OIDC client are on the Quarkus side of the integration. If you want to provide some more general tests, please do :)