Add account management functionality

[daka1510]

Summary

This PR groups changes related to a streamlined account management approach that works across legacy and Cloud accounts and stores configuration data in a JSON file.

Details

This initial PR enables below minimal code paths as per #58.

from qiskit_ibm_runtime import IBMRuntimeService

# Legacy
IBMRuntimeService.save_account(
    auth="legacy",
    name="my-legacy-account",
    token="...",
)

service = IBMRuntimeService(name="my-legacy-account")
service.pprint_programs()
service.active_account()

IBMRuntimeService.saved_accounts()
IBMRuntimeService.delete_account(name="my-legacy-account")

# Cloud
IBMRuntimeService.save_account(
    auth="cloud",
    name="my-cloud-account",
    token="...",
    instance="crn:v1:bluemix:public:quantum-computing:us-east:a/...::",
)

service = IBMRuntimeService(name="my-cloud-account")
service.pprint_programs()
service.active_account()

IBMRuntimeService.saved_accounts()
IBMRuntimeService.delete_account(name="my-cloud-account")

Next Steps

Given that the library is not released yet, I would favor to integrate these changes to enable for more parallelism and avoid additional merge conflicts. In a next step, I will

• add proper unit test coverage for all account management related code paths
• refactor the environment variable names and enable integration tests against a cloud environment

Details and comments

Relates to

• Replace **kwargs with proxies and verify in IBMRuntimeService constructor #48
• Save credentials in JSON file #31

[daka1510]

@rathishcholarajan can you take a look? Are you fine with integrating it at this stage?

PS: Tests fail with the same pattern like all other open PRs. I think those might be caused by a downstream dependency update but given that we're seeing this issue across branches, I am confident that my code changes are not the culprit.

FAILED (failures=6, skipped=3)

[rathishcholarajan]

It’d be nice if IBMRuntimeService is able to delegate Account creation to one class. So the code can be lot simpler here. Something like:

self.account = AccountManager.get(auth, token, url, instance, proxies, verify, name)

[daka1510]

Agree. Planning to consolidate that in a next step by addressing the listed TODOs:

        # TODO: add support for loading default account when optional parameters are not set
        #  i.e. fallback to environment variables
        #  i.e. fallback to default account saved on disk

[rathishcholarajan]

Do we even need a Credentials class? Can it be merged with Account class?

[daka1510]

Agree we don't need the credentials module any longer. I suggest a staged approach to reduce risk and keep the size of the PR reasonable.

[jyu00]

Some minor comments otherwise this is good to go

[daka1510]

@jyu00 addressed your review comments.