Adding a new IRockOwinStartup interface for allowing plugins to implement OWIN functionality.

[cbump]

Contributor Agreement

Have you filled out and sent your Spark Contributor Agreement to secretary [at] sparkdevnetwork.org?
Yes

Context

What is the problem you encountered that lead to you creating this pull request?
We wanted to be able to have plugins hook into OWIN startup in addition to the Application Startup that is already in Rock. OWIN provides additional functionality and a deeper level of access to IIS that isn't available via standard the standard application startup.

Goal

What will this pull request achieve and how will this fix the problem?
This adds the ability for a plugin to hook into OWIN.

Strategy

How have you implemented your solution?
This is essentially the same functionality that already exists with the IRockStartup interface but uses the OWIN architecture instead of the standard Application Startup that the other interface uses.

Tests

If your code is a new method or function (that doesn't need a mock database or SqlServerTypes library) and can be Xunit tested see example be sure your pull request includes the corresponding unit tests in the Rock.Tests project. In all cases you MUST test your code before submitting a pull request.
I don't think we need to provide any additional testing.

Possible Implications

What could this change potentially impact? Are there any security considerations? Where could this potentially affect backwards compatibility?
To my knowledge, this shouldn't affect anything.

Screenshots

Provide us some screenshots if your pull request either alters existing UI or provides new UI. Arrows and labels are helpful.
N/A

Documentation

If your change effects the UI or needs to be documented in one of the existing user guides, please provide the brief write-up here:
We might want to provide a section in the documentation explaining how to add startup functionality with a plugin and when to choose IRockStartup vs IRockOwinStartup: https://www.rockrms.com/Rock/Developer/BookContent/26/26

[azturner]

Looks good.

[azturner]

@cbump I am curious though about what properties you needed from the IAppBuilder param that Owin gives you?

[cbump]

I'm still trying to get a plugin in for a hosted OAuth server into the Rock shop: https://docs.microsoft.com/en-us/aspnet/aspnet/overview/owin-and-katana/owin-oauth-20-authorization-server

You can see it working if you do this:

1. Go here - https://secc.servicereef.com/
2. Click "Sign In" at the top right of the page.
3. Click "Southeast Account" and you'll be presented with a login that's actually hosted in Rock.

We are also planning to use OAuth for mobile authentication as well so we can store a standard OAuth refresh token on a device rather than having to store a password or some other custom token.