Station Settings: Provide fields to store max length configuration for episode/show fields

Since radio hosts are able to edit many fields, the length of its content is critical to displaying them properly on the radio website. Program Managers also to keep them under certain constraints. Depending on the radio station the subtitle field has different ways of use. For some radios it is an actual subtitle, for other it's more like a summary of the description i.e. longer than the meaning of a subtitle.

Therefore, it is suggested to apply a max character count for these fields.

This is the basis for client-site max length validation in Apply max character limit for some fields (dashboard#289 - closed)

Proposal

• Apply the length constraints on API level
• Provide default settings for relevant fields in the configuration and fixtures (radiosettings.json):

        "program": {
            "maxLength": {
                "showName": 60,
                "showShortDescription": 80
                "episodeTitle": 60
                "episodeSummary": 160
            }  
        }

Open questions & considerations

• Where should the length contraints be applied:
  • DB model
  • API (probably favored)
  • client-site
• Counting of characters vs Graphmemes, Unicode, HTML Tags etc. (compare comment 1 and comment 2) - @kmohrf can share some knowlege + library suggestions.
• When no HTML is allowed, then strip the tags