Ensure PG connection is configured before looking up types

Fix: rails#49439

Because Postgres adapter types are connection dependent,
we can't lookup types without first connecting to the database.

Note, this really isn't good, ideally types should be stored in the
schema cache so that we don't have to extract types every time.

Author: byroot

activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb

@@ -149,6 +149,7 @@ def type_cast(value) # :nodoc:
         end
 
         def lookup_cast_type_from_column(column) # :nodoc:
+          verify! if type_map.nil?
           type_map.lookup(column.oid, column.fmod, column.sql_type)
         end
 

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -722,9 +722,7 @@ def initialize_type_map(m) # :nodoc:
       end
 
       private
-        def type_map
-          @type_map ||= Type::HashLookupTypeMap.new
-        end
+        attr_reader :type_map
 
         def initialize_type_map(m = type_map)
           self.class.initialize_type_map(m)