The type or namespace name 'Observer<>' could not be found (are you missing a using directive or an assembly reference?)

The type or namespace name 'Observer<>' could not be found (are you missing a using directive or an assembly reference?)

Process completed with exit code 1.

Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: actions/checkout@v2, actions/setup-dotnet@v1. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

The following actions uses node12 which is deprecated and will be forced to run on node16: actions/checkout@v2, actions/setup-dotnet@v1. For more info: https://github.blog/changelog/2023-06-13-github-actions-all-actions-will-run-on-node16-instead-of-node12-by-default/

'AbstractStore<TState, TMessage>.OnHandleDisposable()' is obsolete

Nullability of reference types in type of parameter 'message' of 'TState MementoStore<TState, TMessage>.Reducer(TState state, TMessage message)' doesn't match the target delegate 'Reducer<TState, TMessage>' (possibly because of nullability attributes).

Nullability of type of parameter 'command' doesn't match overridden member (possibly because of nullability attributes).

'AbstractStore<TState, TMessage>.OnHandleDisposable()' is obsolete

Nullability of reference types in type of parameter 'message' of 'TState MementoStore<TState, TMessage>.Reducer(TState state, TMessage message)' doesn't match the target delegate 'Reducer<TState, TMessage>' (possibly because of nullability attributes).