Ensure that TenantIdResolver does tenantId comparisons without case sensitivity

[christothes]

TenantIdResolver's Resolve method currently compares various forms of tenant Id values to validate and resolve the correct tenantId. These tenantId values should be compared without case sensitivity to be more resilient to odd casing that may come back from a WWW-Authenticate challenge.

There should be additional tests added as well to validate to validate that case insensitive comparisons are being performed.