Fixed: Add tips on how to get service environment variable

[flovntp]

Priority

3 - Not urgent - can be addressed as team bandwidth permits

Where should the changes be made?

https://fixed.docs.upsun.com/add-services/redis.html#use-redis-as-a-handler-for-php-sessions
https://fixed.docs.upsun.com/add-services/valkey.html#use-valkey-as-a-handler-for-php-sessions
and any service pages (Fixed and Flex)

What exactly should be updated?

Fixed:
as service environment variables are not available on Fixed, add a section with the .environment file to grab service envVar value from PLATFORM_RELATIONSHIP and update the service doc pages (Redis and Valkey) but need to check other services.

Flex:
For each service pages, add a section with a .environment snippet on how to define a new <RELATIONSIP>_URL envVar

export SERVICE_URL=${REDIS_HOST}/${REDIS_PORT} 

Optional: Additional context

https://github.com/symfonycorp/cloud-templates/pull/43/files#r2435066178