Added steps explaining token cache on distributed environment

[TiagoBrenck]

Purpose

Apps deployed on distributed environments need to tweak the token cache configuration to be adequate to this architecture. I have added a section exposing available solutions and a code snippet to each of them.

This PR would be an answer for this issue: #158

Does this introduce a breaking change?

[ ] Yes
[x] No

Pull Request Type

What kind of change does this Pull Request introduce?

[ ] Bugfix
[] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[x] Documentation content changes
[ ] Other... Please describe:

How to Test

To be able to test it, you will need 2 different apps deployed on Azure or 1 app with two deployment slots. You cannot test this locally.

What to Check

Verify that both apps are able to grab and save tokens from the cache without any exception being thrown.

Other Information

Resources gotten from:

• https://docs.microsoft.com/en-us/aspnet/core/performance/caching/distributed?view=aspnetcore-2.2
• https://docs.microsoft.com/en-us/aspnet/core/security/data-protection/configuration/overview?view=aspnetcore-2.2

[jennyf19]

[jmprieur]

Thanks @TiagoBrenck
LGTM