Fix schema dumper when datetime infitnity defaults are set

Fixes #40751.

activerecord/lib/active_record/connection_adapters/postgresql/oid/date_time.rb

@@ -16,6 +16,14 @@ module ActiveRecord
               super
             end
           end
+
+          def type_cast_for_schema(value)
+            case value
+            when ::Float::INFINITY then "::Float::INFINITY"
+            when -::Float::INFINITY then "-::Float::INFINITY"
+            else super
+            end
+          end
         end
       end
     end

activerecord/test/cases/schema_dumper_test.rb

@@ -510,6 +510,8 @@ class SchemaDumperDefaultsTest < ActiveRecord::TestCase
       @connection.create_table :infinity_defaults, force: true do |t|
         t.float    :float_with_inf_default,    default: Float::INFINITY
         t.float    :float_with_nan_default,    default: Float::NAN
+        t.datetime :beginning_of_time,         default: "-infinity"
+        t.datetime :end_of_time,               default: "infinity"
       end
     end
   end
@@ -528,10 +530,12 @@ class SchemaDumperDefaultsTest < ActiveRecord::TestCase
     assert_match %r{t\.decimal\s+"decimal_with_default",\s+precision: 20,\s+scale: 10,\s+default: "1234567890.0123456789"}, output
   end
 
-  def test_schema_dump_with_float_column_infinity_default
+  def test_schema_dump_with_column_infinity_default
     skip unless current_adapter?(:PostgreSQLAdapter)
     output = dump_table_schema("infinity_defaults")
     assert_match %r{t\.float\s+"float_with_inf_default",\s+default: ::Float::INFINITY}, output
     assert_match %r{t\.float\s+"float_with_nan_default",\s+default: ::Float::NAN}, output
+    assert_match %r{t\.datetime\s+"beginning_of_time",\s+default: -::Float::INFINITY}, output
+    assert_match %r{t\.datetime\s+"end_of_time",\s+default: ::Float::INFINITY}, output
   end
 end