Beyond simply moving to the builder pattern for intialization this has a
few other effects.
The DeviceFlow and InstalledFlow can no longer be used without an
associated Authenticator. This is becaus they no longer have any
publicly accessible constructor. All initialization goes through the
Authenticator. This also means that the flows are always initialized
with a clone of the hyper client used by the Authenticator.
The authenticator uses the builder pattern which allows omitting
optional fields. This means that if users simply want a default hyper
client, they don't need to create one explicitly. One will be created
automatically. If users want to specify a hyper client (maybe to allow
sharing a single client between different libraries) they can still do so
by using the hyper_client method on the builder. Additionally for both
AuthenticatorDelegate's and FlowDelegate's if the user does not specify
an override the default ones will be used.
The builders are now exposed publicly with the names of Authenicator,
InstalledFlow, and DeviceFlow. The structs that actually implement those
behaviors are now hidden and only expose the GetToken trait. This means
some methods that were previously publicly accessible are no longer
available, but the methods appeared to be implementation details that
probably shouldn't have been exposed anyway.
Specifying a port of zero has the server listen on an ephemeral port.
Many users may not be aware of that unless they have a background in
networking where that's common practice. I'm also not able to think of
any use cases where listening on a hardcoded port would be beneficial,
so with this change I've opted to remove the ability entirely rather
than simply documenting that almost everybody should specify zero.
Change it to accept an iterator of items that can be converted to
`String`s rather than an iterator of items that can be referenced as
`&str`s.
Primarily this allows it to be called with a larger variety of inputs.
For example ::std::env::args().skip(1) can now be passed directly to
token, where before it would first need to be collected into a vector.
Since all implementations unconditionally collected the iterator into a
vector this shouldn't have any negative impact on performance and should
actually reduce the number of allocations in some uses.
It simplifies the signature since the lifetime bounds are no longer
required.
