Inject tags into SRV records

#### Feature Description

Currently, SRV records for a service can only be separated out by changing the service name. This is not possible in some cases (for instance, Puppet uses _x-puppet._tcp.[srv_domain] for service discovery, and there is no way to change anything other than the [srv_domain] portion). Consul already allows for getting A records in the form of .<.tag>.service<.domain>, doing the same with automatic SRV records would bring this into parity with the A records and allow for services to separate clusters.

#### Use Case(s)

This can be used any time multiple separate clusters need provide the same service but must be kept separate during discovery. In the example above of using Puppet, when upgrading from one major Puppet version to another, the ability to tag the version number that a node is providing would make it so clients can be moved between the older and newer revision in a controlled manner.