Use @Nonnull annotations on Java models and generate strict TypeScript

[jonkoops]

Is your feature request related to a problem? Please describe.
Currently we are generating our models based on the Java source from the main Keycloak repo. Since this code is Java all the fields generated in our models are nullable, even if these fields are always present.

This introduces a problem if you are running TypeScript in strict mode, as it will now generate compilation errors when accessing optional fields that are in fact always present. This requires the user to use the non-null assertion operator or to disable strict type checking altogether, introducing possible run-time errors along the way.

Describe the solution you'd like
To mitigate the aforementioned problems we will have to do the following:

• Add @Nonnull or @Nullable annotations to all the fields in models of the main repo
• Use the requiredAnnotations or optionalAnnotations options when generating models

Describe alternatives you've considered
Disable null type checks, this is not a solution.

[edewit]

step one created issue 19740 to change types on keycloak to add the annotations and make the types of the lists / create methods better.