Release 0.26.0

[knope-bot]

Important

Merging this pull request will create this release

Breaking Changes

Change some union variant names

When creating a union with oneOf, anyOf, or a list of type, the name of each variant used to be type_{index}
where the index is based on the order of the types in the union.

This made some modules difficult to understand, what is a my_type_type_0 after all?
It also meant that reordering union members, while not a breaking change to the API, would be a breaking change
for generated clients.

Now, if an individual variant has a title attribute, that title will be used in the name instead.
This is only an enhancement for documents which use title in union variants, and only a breaking change for
inline models (not #/components/schemas which should already have used more descriptive names).

Thanks @wallagib for PR #962!