create basic backend with login

main-server/app/services/jwt_service.rb

@@ -0,0 +1,17 @@
+class JwtService
+  SECRET_KEY = Rails.application.secret_key_base
+  ALGORITHM = "HS256"
+  EXPIRATION = 7.days
+
+  def self.encode(payload)
+    payload[:exp] = EXPIRATION.from_now.to_i
+    JWT.encode(payload, SECRET_KEY, ALGORITHM)
+  end
+
+  def self.decode(token)
+    decoded = JWT.decode(token, SECRET_KEY, true, { algorithm: ALGORITHM }).first
+    HashWithIndifferentAccess.new(decoded).slice(:user_id, :exp)
+  rescue JWT::DecodeError, JWT::ExpiredSignature
+    nil
+  end
+end