OpenAM FreeMarker template injection

OpenAM is an open access management solution. In versions 15.0.3 and prior, the `getCustomLoginUrlTemplate` method in RealmOAuth2ProviderSettings.java is vulnerable to template injection due to its usage of user input. Although the developer intended to implement a custom URL for handling login to override the default OpenAM login, they did not restrict the `CustomLoginUrlTemplate`, allowing it to be set freely. Commit fcb8432aa77d5b2e147624fe954cb150c568e0b8 introduces `TemplateClassResolver.SAFER_RESOLVER` to disable the resolution of commonly exploited classes in FreeMarker template injection. As of time of publication, this fix is expected to be part of version 15.0.4.