support multiple template completion param values and CompleteContext

[jwflicker]

Addresses For Template URI Completions with > 1 substitution variable as a String, each get the same value #31

• In the java mcp impl:
  • request.argument() holds the template variable the completion request is for
  • request.context().arguments() holds the values of the other template variables, if present.
• This change maps these two aspects of the request to the String input parameters...
  • before this, all parameters were set to request.argument().value
• Also lets users inject CompleteRequest.CompleteContext into method params if they want > 3 template substitutions.
• Open questions:
  • do the String method arguments need to be in same order as in template uri?
  • not sure why param names arg0, arg1, etc... so i look to uriVariables for the matching parameter names...
  • not sure if this is validated elsewhere...
  • not sure if any test updates are warranted.
  • Unsure if any side effects against Prompts usage...

[jwflicker]

I still have some doubts whether there is still to much information loss. You still lose which argument is in request.argument()...
maybe we just start with adding CompleteRequest.CompleteContext as an injectable

[tzolov]

@jwflicker
please find thoughts on the subject here: #31 (comment)