EnumDatePreset values being incorrectly serialzied to the URL parameters as upper case

[maxkremer]

Which SDK version are you using?

20.0.0

What's the issue?

Date preset enums EnumDatePreset are being serialized to the graph API URLs parameters as upper case values. Producing a message 100 error

Steps/Sample code to reproduce the issue

      APINodeList<Ad> ads = account.getAds()
                .setParam("date_format", "U") //request dates as epochs
                .setParam("limit", 100) //page size
                .setDatePreset(Ad.EnumDatePreset.VALUE_LAST_90D)
                .requestFields(fields)
                .execute();

Observed Results:

When added to the URL the endpoint complains with the error

{
   "error": {
      "message": "(#100) date_preset must be one of the following values: today, yesterday, this_month, last_month, this_quarter, maximum, data_maximum, last_3d, last_7d, last_14d, last_28d, last_30d, last_90d, last_week_mon_sun, last_week_sun_sat, last_quarter, last_year, this_week_mon_today, this_week_sun_today, this_year",
      "type": "OAuthException",
      "code": 100,
      "fbtrace_id": "Af7UW8liBFkZ_n4YuiC-_KS"
   }
}

You can see from the URL that was built for the request the date_preset is uppercase - manually changing it to lower case produces the correct response from the endpoint

https://graph.facebook.com/v20.0/act_1289608875113430/adsets?limit=100&access_token=XXXXXXXX&date_format=U&appsecret_proof=XXXXXXXXXXX&fields=id%2Caccount_id%2Ccreated_time%2Cupdated_time%2Cend_time%2Ccampaign%2Cbudget_remaining%2Cdaily_budget%2Ceffective_status%2Cname&date_preset=LAST_90D

Expected Results:

I expect the enum values to be serialized to the url in lower case as in last_90d not LAST_90_D