Quotes are not escaped in JSON message

[mbalbus]

Option argstring breaks JSON when some arguments contain quotes.
Please add escaping for placeholders.

Example rundek job that breaks JSON:

- defaultTab: nodes
  description: ''
  executionEnabled: true
  group: ZZZ
  loglevel: INFO
  name: notification-test
  nodeFilterEditable: true
  nodefilters:
    dispatch:
      excludePrecedence: true
      keepgoing: false
      rankOrder: ascending
      successOnEmptyNodeFilter: false
      threadcount: '1'
    filter: ZZZ
  nodesSelectedByDefault: true
  notification:
    onfailure:
      plugin:
        configuration:
          authentication: None
          body: |
            {
              "name": "Args:",
              "value": "${execution.argstring}"
            }
          contentType: application/json
          method: POST
          remoteUrl: http://SOME_SERVER
          timeout: '30000'
        type: HttpNotification
  notifyAvgDurationThreshold: null
  options:
    - name: returnCode
      required: true
      value: 1
    - name: text
      value: '''value in quotes "ZZZ" '''
  plugins:
    ExecutionLifecycle: {}
  scheduleEnabled: true
  schedules: []
  sequence:
    commands:
      - exec: exit ${option.returnCode}
    keepgoing: false
    strategy: node-first