Extension points

phil/instant-messenger

The library is plain PHP and declares no service. What an application adds is messaging services.

`MessengerType`

Phil\InstantMessenger\MessengerType — a service is a case of an enum implementing it. See Services.

Method	Contract
`normalize(string $input): ?string`	The canonical handle the input stands for — a name, an address, a phone number in the service's form — or `null` when it is not one; never throws
`display(string $handle): string`	The canonical handle as people read it
`link(string $handle): ?string`	The address that opens a conversation, or `null` when the service has none

A community forum, a regional network: an enum of the application's own, read and shown its own way, accepted beside KnownMessenger.

Detection

Point	How
Which services are accepted	The `EnumSet`s given to `Messengers::detect()` and `Messengers::handle()`
Which service wins	The order of the sets, then the declaration order of each enum's cases
A handle already canonical	`Handle::fromCanonical()`, for values read back from storage

A service is kept by its enum class and case wherever a handle is stored with it: renaming or removing a case the data still name is a migration of the data.