If API3_MAX_LIMIT set in Heroku config vars, cause V3 api to error

[hamishnorton]

Describe the bug
If you set "API3_MAX_LIMIT": "1000", such as in Heroku config vars, your V3 API errors on every call.

To Reproduce
Steps to reproduce the behavior:

1. Go to 'lib/api3/const.json', set: "API3_MAX_LIMIT": "1000"
2. Call https://<app-name>.herokuapp.com/api/v2/authorization/request/<api-token>
3. Call https://<app-name>.herokuapp.com/api/v3/entries with a valid Bearer token
4. See error in the response: {"status": 500, "message": "Database error"}

Expected behavior
The api call should not error, but instead return data that matches the query.

Your setup information

• NightScout version: "version": "15.0.2"
• Dexcom G7 from AAPS
• Issue is sepecific to Heroku hosting, but it may also affect other hosting if the config vars are set as strings, and not numbers (when it's a number).

Additional context
Modifying `/lib/api3/generic/collection.js ln:70 onwards with...

  self.parseLimit = function parseLimit (req, res) {
    const maxLimit = parseInt(app.get('API3_MAX_LIMIT'), 1000);
    let limit = maxLimit;

    if (req.query.limit) {
      if (!isNaN(req.query.limit) && req.query.limit > 0 && req.query.limit <= maxLimit) {
        limit = parseInt(req.query.limit, 1000);
      }
      else {
        opTools.sendJSONStatus(res, apiConst.HTTP.BAD_REQUEST, apiConst.MSG.HTTP_400_BAD_LIMIT);
        return null;
      }
    }

    return limit;
  };

might work, but I'm not a node/JS guy.
It appears that the code can't cope if the value is a string instead of a number.