okhttp 5.0 async calls

[rfc2822]

Okhttp 5.0 will support async calls (over Kotlin coroutines) – my idea is that dav4jvm will also support this and then provide async calls, too (which can be used by DAVx5 sync algorithm v2)

[rfc2822]

https://square.github.io/okhttp/changelogs/changelog/#version-500-alpha12

Version 5.0.0-alpha.12

Although this release is labeled alpha, the only unstable thing in it is our new APIs. This release has many critical bug fixes and is safe to run in production. We’re eager to stabilize our new APIs so we can get out of alpha.

Maybe not that long anymore ;)

[ArnyminerZ]

For ICSx5 right now we have kept using version 4, and added this TODO

https://github.com/ArnyminerZ/icsx5/blob/77ed3253ae9034fb6ac2e5886ca3928710f600d3/app/build.gradle.kts#L133-L134

Since the coroutines dependency only adds a function.

I've copied it into a separate file until the stable 5.0.0 is released. I don't think that function will change much until the stable version is released, and that way we are not using alpha or beta versions.