Support passing a tenant name for the OAuth endpoint

[trs80]

The authorize and token urls need to be customisable to include a tenant name, to support single-tenant app registration

omniauth-bn-office365/lib/omniauth/strategies/office365.rb

Line 18 in 258b3ef

authorize_url: '/common/oauth2/v2.0/authorize',

https://stackoverflow.com/questions/53526121/use-a-tenant-specific-endpoint-or-configure-the-application-to-be-multi-tenant

[trs80]

https://docs.microsoft.com/en-us/azure/active-directory/develop/active-directory-v2-protocols#endpoints

[babington-andy]

This is pretty critical for me too, without this a user from any office365 tenant can authenticate.

[werk21]

You need to adapt lines 18 and 19:

              authorize_url: '/common/oauth2/v2.0/authorize',
              token_url:     '/common/oauth2/v2.0/token'

to something like this:

              authorize_url: '/mytenant/oauth2/v2.0/authorize
              token_url: '/mytenant/oauth2/v2.0/token

[werk21]

We forked your repo to https://github.com/werk21/omniauth-bn-office365/ and added this feature. Just set OFFICE365_TENANT in ENV.