How to add additional claims to ID Token - Azure Government Portal

I'm trying to overload the OAuth ID Token by adding additional claims. I can already use the Graph API to get the claims that I need but I would like to understand if it's possible to add the additional claims directly into the ID Token? I've updated the manifest by adding the required claims in and then flipping "acceptMappedClaims" to true, however I still don't see these in the ID token. What am I missing?

"optionalClaims": {
    "idToken": [
      {
        "name": "employeeid",
        "source": "user",
        "essential": true,
        "additionalProperties": []
      },
      {
        "name": "mail",
        "source": "user",
        "essential": true,
        "additionalProperties": []
      }
    ],
    "accessToken": [],
    "saml2Token": []
  },
  "acceptMappedClaims": true,

Solution

This depends on where the ID token is generated from. If it's on-premises AD and federated identity is used take a look at Customizing the OIDC id_token in ADFS 2016.

If it's just a cloud identity I'd take a look at the second link jwmiller5 posted or this one: how-to-set-claims-from-asp-net-openid-connect-owin-components.

Hope this helps, Bernie