Force case insensitivity for new emails, existing.

There is a legacy bug I just caught, where many accounts would have the
same email but then have different casing. In extreme scenarios, this
would lead to them creating a new user with the same email, or having
issues with password reset and username lookup.

This doesn't merge in the existing duplicates, but makes sure to only
allow insensitive lowercase emails from here on out. It also will check
for emails in a case insensitive way for such things as resets and
logins if the sensitive lookup doesn't work.

The implementation was not wrong per se - email is supposed to be case sensitive
for usernames. But of course, nobody (nor do most/all email servers) treat
them that way, leading to confusion situations where the user sometimes
camelcases their email and then switches to lowercase later.

models/site.rb

@@ -295,14 +295,23 @@ class Site < Sequel::Model
 
     def get_with_identifier(username_or_email)
       if username_or_email =~ /@/
-        site = self.where(email: username_or_email).where(parent_site_id: nil).first
+        site = get_with_email username_or_email
       else
-        site = self[username: username_or_email]
+        site = self[username: username_or_email.downcase]
       end
       return nil if site.nil? || site.is_banned || site.owner.is_banned
       site
     end
 
+    def get_recovery_sites_with_email(email)
+      self.where('lower(email) = ?', email.downcase).all
+    end
+
+    def get_with_email(email)
+      query = self.where(parent_site_id: nil)
+      query.where(email: email).first || query.where('lower(email) = ?', email.downcase).first
+    end
+
     def ip_create_limit?(ip)
       Site.where('created_at > ?', Date.today.to_time).where(ip: ip).count > IP_CREATE_LIMIT ||
       Site.where(ip: ip).count > TOTAL_IP_CREATE_LIMIT
@@ -844,7 +853,7 @@ class Site < Sequel::Model
 
   def email=(email)
     @original_email = values[:email] unless new?
-    super
+    super(email.nil? ? nil : email.downcase)
   end
 
   def can_email?(col=nil)
@@ -972,12 +981,12 @@ class Site < Sequel::Model
 
     # Check for existing email if new or changing email.
     if new? || @original_email
-      email_check = self.class.select(:id).filter(email: values[:email])
+      email_check = self.class.select(:id).filter('lower(email)=?', values[:email])
       email_check = email_check.exclude(id: self.id) unless new?
       email_check = email_check.first
 
       if parent? && email_check && email_check.id != self.id
-        errors.add :email, 'This email address already exists on Neocities, please use your existing account instead of creating a new one.'
+        errors.add :email, 'This email address already exists on Neocities.'
       end
     end