Updates to work with App Sync Subscriptions

[cmcnally-beachbody]

Task
Closes #1837

Original Discussion - https://github.com/apollographql/apollo-ios/discussions/1820

Summary

• Update to allow for creating custom operation message ids for subscriptions
• Update to writeQueue on start_ack message

[apollo-cla]

@cmcnally-beachbody: Thank you for submitting a pull request! Before we can merge it, you'll need to sign the Apollo Contributor License Agreement here: https://contribute.apollographql.com/

[cmcnally-beachbody]

@designatednerd Here is the update we discussed about two months ago to handle app sync subscriptions

[designatednerd]

I'm at a conference but @calvincestari will be taking a look!

[AnthonyMDev]

Thanks so much for the PR! I'll be honest, I don't know a lot about what this operation id is used for and why we need this PR. Can you explain a little bit about what this PR is trying to do so we can better review it please?

I'm thinking we might want to add some more documentation to this for the future.

[cmcnally-beachbody]

Thanks so much for the PR! I'll be honest, I don't know a lot about what this operation id is used for and why we need this PR. Can you explain a little bit about what this PR is trying to do so we can better review it please?

I'm thinking we might want to add some more documentation to this for the future.

I think this discussion we had started pretty much sums up the why behind needing this change. In our use case we will just be generating UUID strings as the identifiers - #1837

[calvincestari]

@cmcnally-beachbody - it looks like you and @johnclayton both work at the same place and have alignment on this. I want to make sure this solution works for the original request too if that's not the case.

[cmcnally-beachbody]

@cmcnally-beachbody - it looks like you and @johnclayton both work at the same place and have alignment on this. I want to make sure this solution works for the original request too if that's not the case.

Yea we are good, I was just taking the original request over the line and we have just been using our own forked version for a bit.

[calvincestari]

Thanks for the contribution @cmcnally-beachbody and @johnclayton! This will go out with the next release, maybe only next week though as there is another PR we need to get out in that release too.

[cmcnally-beachbody]

Thank you @calvincestari and appreciate the help

[calvincestari]

@cmcnally-beachbody I have a favour to ask if you have the time. I'm working on #2168 which adds support for the graphql-ws protocol and while I was doing that I 'formalized' our support for AppSync. There is no functional change in how the protocol communication behaves for AppSync but if you have the time would you mind pulling that branch into your code and running it through any tests you have for that part of the code. We have integration tests for subscriptionWsProtocol and graphqlWsProtocol but nothing for AppSync.

WSProtocol cases are named according to the protocol not the implementation so while is no named support of AWS AppSync specifically it implements the graphql-ws protocol, with the addition of start_ack which we handle.