auth: Fix appending .default to tenant id scope

[alexweininger]

Fixes #1607

Bug background

These two PRs sorta worked together to introduce this bug. The first started adding .default to the scopes, and the second made it so the scopes are passed through that method twice. Meaning that .default is added to the VSCODE_TENANT the second time the scopes are passed into that method.

• auth: Fix getScopes always injecting the management scope, even if a scope for a different resource is specified #1594
• auth: Make authentication.getSession use scopes argument #1597

The resulting set of scopes will have: ["VSCODE_TENANT:<tenant id>", "VSCODE_TENANT:<tenant id>.default"]. The second entry shouldn't exist and it messes up the built-in authentication provider sometimes since it's not a valid tenant id.

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Solution

The changes I've made make it so that we only call vscode.authentication.getSession in one place. And in that one place is where the scope list is constructed. This avoids any mistakes regarding building the scope list twice.

• Add getSessionFromVSCode helper, which wraps vscode.authentication.getSession and handles constructing the scope list, and adding the VSCODE_TENANT scope.
• Code inside VSCodeAzureSubscriptionProvider do not need to handle scope list creation, they just pass along the tenant id and resource scopes.