It should help catch unicode encoding problems earlier.
This also updates python-saml dependency to a version that includes a
patch for unicode strings.
2. Add site configuration overrides to theming/helpers.py
3. Move microsite.get_value from theming/helpers to site_configuration/helpers
4. Move microsite_configuration.microsite.get_value usages to site_configuration.helpers.values
These changes unify four different approaches to JWT creation, moving the core of the AccessTokenView to a general-purpose JwtBuilder class. This utility class defaults to using the system's JWT configuration, but it will allow overriding of the signing key and audience claim to support those clients which still require this. Part of ECOM-4566.
