[REQ][CSHARP] Make TokenProvider abstract method GetAsync protected for override

[alec-petersen]

Is your feature request related to a problem? Please describe.

It seems users should be able to implement their own functionality for providing a token. The current implementation RateLimitProvider does not accomplish what I am looking for, I'm not going to have a list of tokens at the beginning of program execution, I'm going to need to fetch a token (if the one has expired) and then provide it to the caller

Describe the solution you'd like

This is the current code, I'd like to make the GetAsync public as well as move the ArgumentException thrown here in the constructor to the constructor of the RateLimitProvider class.

    /// <summary>
    /// A class which will provide tokens.
    /// </summary>
    public abstract class TokenProvider<TTokenBase> where TTokenBase : TokenBase
    {
        /// <summary>
        /// The array of tokens.
        /// </summary>
        protected TTokenBase[] _tokens;

        internal abstract System.Threading.Tasks.ValueTask<TTokenBase> GetAsync(string header = "", System.Threading.CancellationToken cancellation = default);

        /// <summary>
        /// Instantiates a TokenProvider.
        /// </summary>
        /// <param name="tokens"></param>
        public TokenProvider(IEnumerable<TTokenBase> tokens)
        {
            _tokens = tokens.ToArray();

            if (_tokens.Length == 0)
                throw new ArgumentException("You did not provide any tokens.");
        }
    }

Describe alternatives you've considered

I could put a new implementation in the generated code, but I still think it makes sense to have this behavior extendable by users without making the internals visible.

I am happy to do this work and open a PR.

[devhl-labs]

You can already provide your own TokenProvider, so you should not be blocked. See options.UseProvider<RateLimitProvider<BearerToken>, BearerToken>(); in the README. I don't see why GetAsync should be public since it only needs to be called internally. I am open to removing the ArgumentException if we add a way to append tokens after construction.

edit-I guess you can't inherit the abstract TokenProvider while it has an internal abstract, can you? Yeah, I guess it needs to change then. I think protected internal would work.

[alec-petersen]

@devhl-labs Sounds good, just opened a PR.