Fix error thrown by PG when lowercasing an int (#2655)

* ensure passed variable is a string

* revise paramater sanitizing to occur in identifier rather than user

Co-authored-by: Brian Riley <brian.riley@ucop.edu>

Author: xsrust

app/models/identifier.rb

@@ -46,8 +46,9 @@ class Identifier < ActiveRecord::Base
   # = Scopes =
   # ===============
 
-  def self.by_scheme_name(value, identifiable_type)
-    where(identifier_scheme: IdentifierScheme.by_name(value),
+  def self.by_scheme_name(scheme, identifiable_type)
+    scheme_id = scheme.instance_of?(IdentifierScheme) ? scheme.id : IdentifierScheme.by_name(scheme).first&.id
+    where(identifier_scheme_id: scheme_id,
           identifiable_type: identifiable_type)
   end