Context:
The environment variable introduced in OPT-6957 still has to be added to the optimize helm chart.

AT:

• optimize helm chart sets CAMUNDA_OPTIMIZE_IDENTITY_REDIRECT_ROOT_URL 
• this change needs to be backported to 3.9 helm charts

Testing notes:

• Note that this relates to the variable added with OPT-6957, it can probably be tested at the same time
• When the redirect url is defined via the helm chart, this is correctly respected by Identity during authentication callback
• https://github.com/camunda/camunda-platform-helm/tree/main#installation