Token migrations

[kevinavery]

Introduces token migration for client sessions created with older versions of this library.

Upgrading the library might result in previous session tokens failing to decode, resulting in users being logged out. Now there are configuration settings to enable token migration to the current version.

I've only considered v0.5.0 -> v0.5.3 (current):

• No token changes were made from v0.5.0 -> v0.5.1.
• On v0.5.2, the signature changed: c143365...release-0.5.2
• On v0.5.3 the multi-value serializer changed: release-0.5.2...6f67a92

These are the added configs:

akka.http.session {
  ...
  token-migration {
    v0-5-2 {
      enabled = false
    }
    v0-5-3 {
      enabled = false
    }
  }
}

If you're upgrading from v0.5.1 to v0.5.3 (current), you should enable migrations for both v0.5.2 and v0.5.3. If you're upgrading from v0.5.2, you only need to enable the v0.5.3 migration.

[adamw]

0.5.4 released - thanks for your work! I only made one small change, making SessionSerializer a trait again.

[kevinavery]

👍 thanks! When do you expect it to be published to the maven repo?

[adamw]

🤦‍♂️ forgot to publish for 2.12. Should be there in 15 minutes max