Split out SimpleEmailEventsReceiptAction into different action types

[craigbrett17]

Description of changes:

We were trying to use this library to allow us to have a lambda handle emails being received with an S3 action. However, the library as was only supports Lambda. So we're currently using dynamic to get around this limitation, but I'd rather be type safe.

So, what I've done, is split the SimpleEmailReceiptAction into an interface and 2 different action types. This type can then be passed in as a <T> at any level of the nested classes, and will resolve properly. Unit tests confirm.

It would help us be type safe were this request to be confirmed.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[normj]

Thanks for the PR. I would like to include the PR but we need to find a way that isn't a breaking change,

One option would be to have a non generic version of SimpleEmailEvent that extends from SimpleEmailEvent<LambdaReceiptAction>. Something like this.

public interface IReceiptAction
{
    string Type { get; set; }
}

public class LambdaReceiptAction : IReceiptAction
{
    public string Type { get; set; }
}

public class S3ReceiptAction : IReceiptAction
{
    public string Type { get; set; }
}

public class SimpleEmailEvent<TReceiptAction> where TReceiptAction : IReceiptAction
{

}

public class SimpleEmailEvent : SimpleEmailEvent<LambdaReceiptAction>
{

}


class Program
{
    static void Main(string[] args)
    {
        var nonBreaking = new SimpleEmailEvent();
        var lambdaBreaking = new SimpleEmailEvent<LambdaReceiptAction>();
        var s3Event = new SimpleEmailEvent<S3ReceiptAction>();
    }
}

We could mark the non generic SimpleEmailEvent as Obsolete with a message explaining why there is a non generic and that they should use the generic version.

[craigbrett17]

@normj: Alright, I've gone with what you suggested and implemented some lambda by default backwards compatible types. Hopefully the obsolete message will be enough to encourage people to make the hopefully painless change over. 🤞

[normj]

I have merged this into the dev branch to go out with the next release.

[normj]

Version 2.0.0 of Amazon.Lambda.SimpleEmailEvents has been released with this PR