[Design] Why `ContextInjector` is an internal API

[GeorgePap-719]

What do we have today?

ContextInjector is an internal API.

Why does this feel problematic?

I am required to implement it for creating proper glu-code with the jooq library, which uses its own implementations of the Publisher interface.

@OptIn(InternalCoroutinesApi::class)
class JooqContextInjector : ContextInjector {
    @Suppress("UNCHECKED_CAST")
    override fun <T> injectCoroutineContext(publisher: Publisher<T>, coroutineContext: CoroutineContext): Publisher<T> {
        val reactorContext = coroutineContext[ReactorContext]?.context ?: return publisher
        return when (publisher) {
            is Mono -> publisher.contextWrite(reactorContext)
            is Flux -> publisher.contextWrite(reactorContext)
            // Bridge with jooq:
            // `Flux.from(publisher)` is jooq's documented way to turn its bridge `Publisher` into something Reactor-native.
            // Though, wrapping alone only gets us a real Flux; the context still needs a path into jooq's internals.
            // That path is the `SubscriberProvider` SPI, see `ReactorSubscriberProvider`.
            else -> Flux.from(publisher as Publisher<Any>).contextWrite(reactorContext) as Publisher<T>
        }
    }
}

Is there another way to implement the bridge code without using the ContextInjector API?