mongodb create admin user for all databases

use admin
db.createUser(
      {
          user: "username",
          pwd: "password",
          roles: [ "root" ]
      }
  )

use admin
db.createUser({ user: "mongoadmin" , pwd: "mongoadmin", roles: ["userAdminAnyDatabase", "dbAdminAnyDatabase", "readWriteAnyDatabase"]})