Abuse of Api that causes spamming users and possible DOS due to missing rate limit

##Summary: In your sub-domain: http://demo.weblate.org , another endpoint doesn't have any rate limit on it to prevent spamming you by posting a lot of questions. ##Description: Spamming and Possible DOS is being possible due to missing rate limit on this endpoint. **Request** POST /accounts/email/ HTTP/1.1 Host: demo.weblate.org User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Firefox/52.0 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Language: en-US,en;q=0.5 Accept-Encoding: gzip, deflate, br Referer: https://demo.weblate.org/ Cookie: XXX Connection: close Upgrade-Insecure-Requests: 1 Content-Type: application/x-www-form-urlencoded Content-Length: 126 csrfmiddlewaretoken=&email=victim_email&content=