Jenkinsfile for a multibranch-pipeline project that builds and deploys a rails application - using capistrano and rvm on jenkins-server

Jenkinsfile

// jenkinsfile - as declarative pipeline

pipeline {
  agent any

  environment {
    // credentials 'jenkins-db-credential' is globally accessible on jenkins
    //
    DB_CREDENTIAL = credentials('jenkins-db-credential')
    DB_USER = "${env.DB_CREDENTIAL_USR}"
    DB_PASS = "${env.DB_CREDENTIAL_PSW}"
    RAILS_ENV = 'test'
  }

  stages {
    stage("prepare") {

      steps {
        // credentials 'rails-master-key' have to be present
        // for this specific multibranch-pipeline
        withCredentials([string(credentialsId: 'rails-master-key', variable: 'RAILS_MASTER_KEY')]) {
          echo 'preparing sch_net build'

          sh 'echo "test:\n  adapter: postgresql\n  database: sch_net_test\n  username: $DB_USER\n  passsword: $DB_PASS" > ./config/database.yml'

          sh '''#!/bin/bash -l
            rvm use ruby-2.6.5
            gem install bundler
            bundle install
            ./bin/rails db:reset
          '''
        }
      }
    }

    stage("test") {

      steps {
        withCredentials([string(credentialsId: 'rails-master-key', variable: 'RAILS_MASTER_KEY')]) {
          echo 'testing sch_net'

          sh '''#!/bin/bash -l
            rvm use ruby-2.6.5
            ./bin/rails test
          '''
        }
      }
    }

    stage("deploy staging") {

      when {
        expression {
          env.BRANCH_NAME == 'staging'
        }
      }
      steps {
        echo 'deploying staging'
        sh '''#!/bin/bash -l
          rvm use ruby-2.6.5
          bundle exec cap staging deploy
        '''

      }
    }

    stage("deploying production") {

      when {
        expression {
          env.BRANCH_NAME == 'master'
        }
      }
      steps {
        echo 'deploying master'
        sh '''#!/bin/bash -l
          rvm use ruby-2.6.5
          bundle exec cap production deploy
        '''

      }
    }
  }

  post {
    always {
      echo 'always after sch_net'
    }
    success {
      echo 'after success sch_net'
    }
    failure {
      echo 'after failure sch_net'
    }
  }
}