Passing Data to IProfileService in IdentityServer4 - asp.net-core

Question

I am using IdtentityServer4 where I have a scenario when a support personnel want to login on behalf of a user for support.
When this happens I want to know throughout my ASP.NET Core app that this support guy is acting on behalf of the user with a message on the screen that says:
"Mr Support on Behalf of Ms Username"
I am currently implementing IProfileUser for normal login. I am looking for a way to add an extra "attribute" to include the username of the support person in token without accessing the database.
I tried to pass items
await _signInManager.SignInAsync(applicationUser, new AuthenticationProperties
{
Items = {new KeyValuePair<string, string>("SupportName", "Mr Support")}
}).ConfigureAwait(false);
But I don't know how to get them from the ProfileDataRequestContext passed to GetProfileDataAsync in IProfileService implementation.
This is my IProfileService implementation:
public async Task GetProfileDataAsync(ProfileDataRequestContext context)
{
ClaimsPrincipal claimsPrincipal = context.Subject;
if (claimsPrincipal == null)
{
throw new ArgumentNullException(nameof(context.Subject));
}
string id = claimsPrincipal.GetSubjectId();
ApplicationUser user = await _userManager.FindByIdAsync(id).ConfigureAwait(false);
if (user == null)
{
throw new ArgumentException("Invalid user identifier");
}
context.IssuedClaims.Add(new Claim(JwtClaimTypes.Email, user.Email));
IList<string> roles = await _userManager.GetRolesAsync(user).ConfigureAwait(false);
foreach (var role in roles)
{
context.IssuedClaims.Add(new Claim(JwtClaimTypes.Role, role));
}
context.IssuedClaims.Add(new Claim(JwtClaimTypes.Name, user.Name));
}

Answer 1

You could pass this data via a claim.
Modify your sign-in code to include the "SupportName" claim:
// Sign in the user and include the SupportName claim
await HttpContext.SignInAsync(userId, username, new Claim("SupportName", "Mr Support"));
and access this claim in GetProfileDataAsync:
public async Task GetProfileDataAsync(ProfileDataRequestContext context) {
// Find the "SupportName" claim added during sign-in
var supportNameClaim = context.Subject.FindFirst("SupportName");
if (supportNameClaim != null) {
Console.WriteLine($"Signed in on behalf of {supportNameClaim.Value}");
}
// Issue all the claims (if required)
context.IssuedClaims.AddRange(context.Subject.Claims);
}