get https://{tenanturl}/v1.0/branding/themes
List of all the themes that are registered for the tenant.
This generates a list of registered themes for the tenant, which includes the theme name and description(optional).
The default theme is always present since it is the current themeID for your Verify tenant.
Entitlements required:
manageTemplates (Manage templates and themes) or readTemplates (Read templates and themes)