This release fixes an incorrect optimisation in
`Doctrine\DBAL\Query\Expression\CompositeExpression` which
could have led to dropping query expression components.

Also, DBAL was ignoring some important platform settings
when determining which cache keys to use when looking for
result caches: that could have led to sharing caches for
results produced by different DB connections.

Total issues resolved: **2**

- [2785: Fix `CompositeExpression#add()` optimization, which was leading to broken `CompositeExpression` instances](https://github.com/doctrine/dbal/pull/2785) thanks to @Grzesie2k
- [2821: Platform from params are not correctly passed to a `QueryCacheProfile`](https://github.com/doctrine/dbal/pull/2821) thanks to @kimhemsoe