use admin

db.createUser(
{
    user: "root",
    pwd: "abc123",
    roles: [
    {
        role: "root",
        db: "admin"
    }]
})

use project_db

db.createUser(
{
    user: "project_admin",
    pwd: "def456",
    roles: [
    {
        role: "dbOwner",
        db: "project_db"
    }]
})

mongo --username project_admin
      --password def456
      --authenticationDatabase project_db
    < "${path_to_db_build_script}"

db = connect("localhost:27017/project_db");
db.getSiblingDB("project_db").auth("project_admin", "def456");

db.auth("project_admin", "def456")

db.auth({ user: "project_admin", pwd: "def456" })

db.auth({ user: "project_admin", pwd: "def456", digestPassword: fails })

db.auth({ user: "project_admin", pwd: "def456", digestPassword: true })

db.auth({ user: "project_admin", pwd: "def456", digestPassword: true, mechanism: "PLAIN" })

db.auth({ user: "project_admin", pwd: "def456", digestPassword: fails, mechanism: "SCRAM-SHA-1" })

db.auth({ user: "project_admin", pwd: "def456", digestPassword: true, mechanism: "SCRAM-SHA-1" })

mongo admin -u root -p abc123

...
{
    "_id": "project_db.project_admin",
    "user": "project_admin",
    "db": "project_db",
    "credentials":
    {
        "SCRAM-SHA-1":
        {
            "iterationCount": 10000,
            "salt": "WnKFmGs3BTbmkbUWi0RPnA==",
            "storedKey": "EEIMqBEMUUOpoR3i3pgKz0iRumI=",
            "serverKey": "HsSOxujNODlKcRiEdi1zkj83MRo="
        }
    },
    "roles": [
    {
        "role": "dbOwner",
        "db": "project_db"
    }]
}
  ...