Salesforce provider has incorrect property name

[martincostello]

While looking into additional tests for #280 (see #282), I found that the name claim used is different compared to the Salesforce documentation.

In the provider, "user_name" is used.

AspNet.Security.OAuth.Providers/src/AspNet.Security.OAuth.Salesforce/SalesforceAuthenticationOptions.cs

Line 30 in 8b1b82e

ClaimActions.MapJsonKey(ClaimTypes.Name, "user_name");

In the documentation, "username" is used.

The example does not actually contain either "user_name" or "username", so I'm unable to easily verify whether this is a code issue or a docs issue.

[martincostello]

Assuming the docs are correct, fix would be something like this: martincostello@953a998

[martincostello]

From testing, the claim key is incorrect. It should be "username".

Fixed in 953a998.