How to use volumemounts with configmaps

gistfile1.txt

---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: app
  name: app
  namespace: portals
spec:
  progressDeadlineSeconds: 600
  replicas: 1
  revisionHistoryLimit: 10
  selector:
    matchLabels:
      app: app
  strategy:
    rollingUpdate:
      maxSurge: 25%
      maxUnavailable: 25%
    type: RollingUpdate
  template:
    metadata:
      labels:
        app: app
    spec:
      containers:
      - env:
        - name: JAVA_OPTS
          value: "-Dspring.config.location=/app/resources"
        envFrom:
        - configMapRef:
            name: oauth-config
            optional: false
        - configMapRef:
            name: app-config
            optional: false
        - secretRef:
            name: mongodb-secret
            optional: false
        - secretRef:
            name: mysql-secret
            optional: false
        - secretRef:
            name: app-secret
            optional: false
        image: something:1.0.0
        ##### FOR DEBUGGING PURPOSES
        # command: [ "/bin/bash", "-c", "--" ]
        # args: [ "while true; do sleep 30; done;" ]
        imagePullPolicy: Always
        name: app
        resources: {}
        securityContext:
          allowPrivilegeEscalation: false
          capabilities: {}
          privileged: false
          readOnlyRootFilesystem: false
          runAsNonRoot: false
        stdin: true
        terminationMessagePath: /dev/termination-log
        terminationMessagePolicy: File
        tty: true
        volumeMounts:
        - mountPath: /opt/app-root/config
          name: app
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      schedulerName: default-scheduler
      securityContext: {}
      terminationGracePeriodSeconds: 30
      volumes:
      - configMap:
          defaultMode: 256
          items:
          - key: application.properties
            path: application.properties
          name: app-config
          optional: false
        name: app
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
  namespace: portals
data:
  application.properties: |-
    # active-profile=default
    logging.level.web=TRACE
    logging.level.org.springframework.web.server=TRACE
    logging.level.org.apache.coyote.http11.Http11InputBuffer=DEBUG
    logging.level.org.springframework.web.cors=TRACE
    logging.level.org.springframework.web.servlet.DispatcherServlet=DEBUG.
    logging.level.org.apache.tomcat.util.http.Rfc6265CookieProcessor=DEBUG