Add Steam OpenID authentication

microservices/AuthApi/Services/JwtTokenService.cs

@@ -0,0 +1,33 @@
+using AuthApi.Models;
+using Microsoft.IdentityModel.Tokens;
+using System.IdentityModel.Tokens.Jwt;
+using System.Security.Claims;
+using System.Text;
+
+namespace AuthApi.Services;
+
+public class JwtTokenService
+{
+    private readonly IConfiguration _cfg;
+
+    public JwtTokenService(IConfiguration cfg) => _cfg = cfg;
+
+    public (string Token, string Jti, DateTime ExpiresUtc) Generate(User user)
+    {
+        var key = Encoding.UTF8.GetBytes(_cfg["Jwt:Key"] ?? throw new InvalidOperationException("Jwt:Key missing"));
+        var issuer = _cfg["Jwt:Issuer"] ?? "GameAuthApi";
+        var audience = _cfg["Jwt:Audience"] ?? issuer;
+        var credentials = new SigningCredentials(new SymmetricSecurityKey(key), SecurityAlgorithms.HmacSha256);
+        var jti = Guid.NewGuid().ToString("N");
+        var claims = new[]
+        {
+            new Claim(ClaimTypes.Name, user.Username),
+            new Claim(ClaimTypes.NameIdentifier, user.Id),
+            new Claim(ClaimTypes.Role, user.Role),
+            new Claim(JwtRegisteredClaimNames.Jti, jti)
+        };
+        var expiresUtc = DateTime.UtcNow.AddMinutes(15);
+        var token = new JwtSecurityToken(issuer, audience, claims, expires: expiresUtc, signingCredentials: credentials);
+        return (new JwtSecurityTokenHandler().WriteToken(token), jti, expiresUtc);
+    }
+}