Introduce Discovery error saying that static registration is required

[Michael Jones]

As recorded in issue #604, Breno suggested that we may want a discovery error saying that static registration is required. Ideally, the error message would also direct people to where this registration could be performed.

The case might also be able to be made for a discovery result returning this information instead or additionally.

[Michael Jones]

We will add a service_documentation field to the discovery result

[Michael Jones]

Fixed #697 - Added service_documentation to enable OPs not supporting dynamic registration to say how to register clients

→ <<cset 34c6df7f3ce7>>