Vivox Unity SDK 16.8.0

For further technical details on all the changes included in this release, refer to the `CHANGELOG.md` file within the SDK.

Fixed a memory leak caused by unbound event handlers preventing `VivoxParticipant` objects from being cleaned up when the local user left channels with remaining participants.

`VivoxMessage.Metadata` property for accessing channel or directed message metadata.

`MessageOptions.Metadata` property for attaching metadata to outgoing messages.

Added automatic SDK initialization and user sign-in when SDK actions are attempted without prior setup.

Added support for multiple concurrent Vivox SDK instances via `IUnityServices.GetVivoxService()` .

Removed Mint service integration and deprecated related public APIs.

Updated minimum supported Editor version to 2021.3.

Updated Services Core SDK dependency version.

Some Bluetooth audio devices on Windows will have reduced audio quality because the operating system forces them into Handsfree Telephony mode. This will be fixed in the next hotfix release.

• Windows

Added `ChannelOptions.IsLargeText` to allow a channel to be configured as a large text channel. With this feature enabled, text channels can support up to 2000 users.

Fixed an issue that was restricting the usage of dots in channel names and player IDs.

Fixed an issue that would cause a `NullReferenceException` when trying to use mute, volume, or device-related APIs while not signed in to the Vivox service.