Implement asynchronous support in ODataNotificationReader

[gathogojr]

Issues

This pull request partially fulfills #2019.

Description

Implement asynchronous support in ODataNotificationReader.

Checklist (Uncheck if it is not completed)

• Test cases added
• Build and test with one-click build and test script passed

Additional work necessary

If documentation update is needed, please add "Docs Needed" label to the issue and provide details about the required document change in the issue.

[habbes]

I have some concerns regarding the ownership of the wrapped TextReader. You mention in the comments that it should not be disposed by the ODataNotificationReader since it's not the owner. However, in the original version, the ODataNotificationReader did dispose of the TextReader. Can you confirm that your changes are the expected behaviour and the previous implementation was a bug?

I have found the following scenario where an ODataNotificationReader is created:

public override sealed TextReader CreateTextReader()
{
    if (this.State == ODataReaderState.Stream)
    {
        /* ... omitted for brevity */
        return new ODataNotificationReader(this.InterceptException(this.CreateTextReaderImplementation), this);
    }
    else
    {
        throw new ODataException(Strings.ODataReaderCore_CreateTextReaderCalledInInvalidState);
    }
}

Here, a TextReader is created inline and passed directly to the ODataNotificationReader constructor. There's no other reference left for the TextReader. So if the ODataNotificationReader does not dispose it, then TextReader will not be disposed as there's no other object which has a reference to it. And the calling method will only get back a reference of the ODataNotificationReader since that's the return value, and will have no idea that it's wrapping another TextReader given that the return type is simply TextReader.

If ODataNotificationReader is not the owner, then that logic should be refactored such to ensure TextReader gets properly disposed. If ODataNotificationReader is the owner (and the above snippet suggests that it is), then it should dispose of TextReader. In either case, I think the doc comments of ODataNotificationReader should be updated to mention whether or not it assumes the ownership responsibility of disposing TextReader.

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This PR has 135 quantified lines of changes. In general, a change size of upto 200 lines is ideal for the best PR experience!

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Total files changed: 2

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.cs : +128 -7

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