Validate Principal should accept Unresolved

[jjrawlins]

Describe the bug
A clear and concise description of what the bug is.
When using the construct, user should be able to create an assignment using the following structure

 const group = new CfnGroup(this, `${groupName}`, {
        displayName: groupName,
        identityStoreId: SsoIdentityStoreId,
        description: groupName,
      });

      accountIds?.forEach((accountId) => {
        new Assignment(this, `${accountId}-${groupName}`, {
          permissionSet: permissionSet,
          principal: {
            principalId: group.attrGroupId,
            principalType: PrincipalTypes.GROUP,
          },
          targetId: accountId,
        });
      });

To Reproduce
Steps to reproduce the behavior:

1. Go to line 5 in principal-common.ts
2. Currently only tests for
   if (!principal.principalId.match(/^([0-9a-f]{10}-|)[A-Fa-f0-9]{8}-[A-Fa-f0-9]{4}-[A-Fa-f0-9]{4}-[A-Fa-f0-9]{4}-[A-Fa-f0-9]{12}$/)) {
   throw new Error(PrincipalId must be a valid GUID: ${principal.principalId});
   }

Expected behavior
A clear and concise description of what you expected to happen.

Should test for unresolved

if (!Token.isUnresolved(principal.principalId) && !principal.principalId.match(/^([0-9a-f]{10}-|)[A-Fa-f0-9]{8}-[A-Fa-f0-9]{4}-[A-Fa-f0-9]{4}-[A-Fa-f0-9]{4}-[A-Fa-f0-9]{12}$/)) {
throw new Error(PrincipalId must be a valid GUID: ${principal.principalId});
}

This will allow users to create their own UserGroups and pass in the unresolved token to the Assignment Object.

[bmiller08]

This should now be resolved in 0.1.150

[bmiller08]

See d01e11d for specific fix.