Add authentication function

Signed-off-by: Asai Neko <sugar@sne.moe>

service/auth/handler.go

@@ -0,0 +1,8 @@
+package auth
+
+import "github.com/gin-gonic/gin"
+
+func Handler(r *gin.RouterGroup) {
+	r.POST("/magic", RequestMagicLink)
+	r.GET("/magic/verify", VerifyMagicLink)
+}