We will let Azure Active Directory know about IntelliGantt here so all your users can access it.
This is a one time, initial setup performed by the administrator. Users will simply go to www.intelligantt.com/sharepoint.
Azure Active Directory provides the ability to grant access for applications to use Office 365 API. Without this step IntelliGantt will not be able to access your data in SharePoint.com.
By default the Azure Active Directory is provisioned for you.
We're talking to SharePoint first, but my those other APIs look interestering too!
This gives the currently logged in user their permission profile to your sharepoint.com site.
This is deep in the bowels gobbledeegook that lets the user permissions work through the rest api calls.
Azure Active Directory is all set up, now we just need to let IntelliGantt know about it.
This can be the root or any subsite you like. Subsites can be a little trickier as it's not always clear what the actual site endpoint to use is. In general, it's everything before the 'SitePages/Home.aspx' part of your url.
Whether you want to connect to the top level site or a subsite, the first time you need to pair 'yourcompany'.sharepoint.com to an Application ID. Again, a one-time only step no one else will see.
Be sure your web browser allows popups for the www.intelligantt.com site otherwise you won't see this page. When you do see it, this login is from microsoftonline.com and thus supports all the login options you have set up, like two-factor authentication.
The delegated permission we assigned in Azure Active Directory is reflected here for the user to agree with. Click 'Accept' and IntelliGantt will be able to access your task lists, tasks and subsites for all your project management and aggregation needs!
Edge and IE 10/11 may require you to make sure both https://login.microsoftonline.com and https://www.intelligantt.com are in your Trusted Zones.
Something or other to do with cookies apparently. Chrome, Firefox and Safari work just fine.