Multi destination

[jhlee-mitre]

Implemented a new feature to handle multi-destination in TestScript.

Detail:

1. In driver.rb changed endpoint to Array to store multiple server addresses. I put seven predefined, different server addresses from HAPI, Firely, and Logica. We need to start discussion of how to deal with multiple server addresses. Questions may include 1) when we have multiple destinations, should they be always different servers or server instances? 2) What if 100 multiple destinations in TestScript? Should the engine get prepared for 100 server addresses? 3) Do we keep server address in hard coded way as it is, or would we create a configuration file for the engine (e.g. configure.xml)?

2. Client object corresponds to destination. If there are two destinations in TestScript, the engine instantiates two Clients. If a TestScript doesn't include destination, the engine considers to use "default" client, which picks the first one from the server address list in endpoints.

3. Client object is moved from TestScriptEngine.rb to TestScriptRunnable.rb, since now one client won't be used by multiple runnables. Each runnable should have own instance of Client correspond to destination.

4. The engine reads multiple origins but doesn't do anything with it for now.

Additional:

1. Example TestScript for multi-agent is added.

[jawalonoski]

Hard-coding the server list doesn't make sense to me. Since it is a command-line tool, I would expect the user to list the servers they want to use as arguments. Acceptable alternatives include writing a shell script for frequently used scenarios or creating a configuration file.

The user wants to run a TestScript with 2 destinations? Then they are required to provide two URLs.

The engine shouldn't run if an endpoint is not specified.

It doesn't matter if the array is size 1 or size 1 billion. Other than memory. And you'd need a scenario that has that many endpoints. But it shouldn't matter.

[jhlee-mitre]

1. If no server address entered in argument, default server is assigned.
2. If one server address entered in argument, it replaces default server.
3. If there are destination in TestScript, servers are assigned to destinations in order in argument
4. If # of server address < destination, the engine errors.

Test with these:

ruby driver.rb read_test_script.json  
ruby driver.rb http:https://hapi.fhir.org/baseR4 read_test_script.json
ruby driver.rb http:https://hapi.fhir.org/baseR4 multisystem_test_script.json
ruby driver.rb http:https://hapi.fhir.org/baseR4 https://server.fire.ly/ multisystem_test_script.json
ruby driver.rb http:https://hapi.fhir.org/baseR4 https://server.fire.ly/ read_test_script.json

[ms-k1ngk0ng]

Nice! I think the biggest change needed is how/when we prompt users for endpoints. I've included my thoughts, but if any of it is unclear, let me know and we can discuss.

[jhlee-mitre]

Close this PR by end of the project. Issue #53 will keep open without milestone.