IQSS/10516 fix perma legacy support

[qqmyers]

What this PR does / why we need it: Fixes handling of legacy permalink configuration after the multi pid upgrade. Two underlying issues: base-url wasn't optional as it used to be and the identification of a legacy perma provider for a give PID was broken due to use of the wrong default separator.

Which issue(s) this PR closes:

Closes #10516

Special notes for your reviewer:

Suggestions on how to test this: Setup a legacy perma config using :Authority, :Shoulder, :Protocol and confirm it works (Dataverse starts, can create/publish datasets). Note that now that Dataverse requires a valid PID config to start and you can't use the settings API until Dataverse has started, you either need to configure and then remove a multipid config, or update the settings in the DB directly.

Does this PR introduce a user interface change? If mockups are available, please link/include them here:

Is there a release notes update needed for this change?: added

Additional documentation:

[coveralls]

coverage: 22.576% (+0.005%) from 22.571% when pulling 554adfa19ffbdb378b52e320759ee49e72e96846 on GlobalDataverseCommunityConsortium:IQSS/10516_fix_perma-legacy_support into a4d01270da53e1d76420c3f607a699f05e59fa8c on IQSS:develop.

[ofahimIQSS]

Fix looks good, no issues found during regression testing.