Add toggle method to control use_minimum_char_limit

Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/348509
Changelog: changed

app/models/user.rb

@@ -717,13 +717,17 @@ class User < ApplicationRecord
         .take(1) # at most 1 record as there is a unique constraint
 
       where(
-        fuzzy_arel_match(:name, query)
-          .or(fuzzy_arel_match(:username, query))
+        fuzzy_arel_match(:name, query, lower_exact_match: false, use_minimum_char_limit: use_minimum_char_limit_toggle)
+          .or(fuzzy_arel_match(:username, query, lower_exact_match: false, use_minimum_char_limit: use_minimum_char_limit_toggle))
           .or(arel_table[:email].eq(query))
           .or(arel_table[:id].eq(matched_by_email_user_id))
       )
     end
 
+    def use_minimum_char_limit_toggle
+      true
+    end
+
     def by_login(login)
       return unless login
 

spec/models/user_spec.rb

@@ -2538,6 +2538,12 @@ RSpec.describe User do
     end
   end
 
+  describe '.use_minimum_char_limit_toggle' do
+    it 'returns true' do
+      expect(described_class.use_minimum_char_limit_toggle).to be true
+    end
+  end
+
   describe '.find_by_ssh_key_id' do
     let_it_be(:user) { create(:user) }
     let_it_be(:key) { create(:key, user: user) }