Setup basic code for login.

API/Services/TokenService.cs

@@ -0,0 +1,46 @@
+using System;
+using System.Collections.Generic;
+using System.IdentityModel.Tokens.Jwt;
+using System.Security.Claims;
+using System.Text;
+using API.Entities;
+using API.Interfaces;
+using Microsoft.Extensions.Configuration;
+using Microsoft.IdentityModel.Tokens;
+using JwtRegisteredClaimNames = Microsoft.IdentityModel.JsonWebTokens.JwtRegisteredClaimNames;
+
+
+namespace API.Services
+{
+    public class TokenService : ITokenService
+    {
+        private readonly SymmetricSecurityKey _key;
+
+        public TokenService(IConfiguration config)
+        {
+            _key = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(config["TokenKey"]));
+        }
+
+        public string CreateToken(AppUser user)
+        {
+            var claims = new List<Claim>
+            {
+                new Claim(JwtRegisteredClaimNames.NameId, user.UserName)
+            };
+            
+            var creds = new SigningCredentials(_key, SecurityAlgorithms.HmacSha512Signature);
+
+            var tokenDescriptor = new SecurityTokenDescriptor()
+            {
+                Subject = new ClaimsIdentity(claims),
+                Expires = DateTime.Now.AddDays(7),
+                SigningCredentials = creds
+            };
+            
+            var tokenHandler = new JwtSecurityTokenHandler();
+            var token = tokenHandler.CreateToken(tokenDescriptor);
+
+            return tokenHandler.WriteToken(token);
+        }
+    }
+}