Oracle Bulk Create TextField fails when there is a mix of short and long string

[Ahmet Kucuk]

Following test currently fails because oracle DB backend converts params larger than 4000 to be CLOB.

class OracleTextFieldBulkCreateTests(TestCase):
    @unittest.skipIf(connection.vendor != 'oracle', 'Only an oracle issue')
    def test_text_field_bulk_create(self):
        m1 = ModelD(name='a'*4001)
        m2 = ModelD(name='a')
        ModelD.objects.bulk_create([m1, m2])

DatabaseError: ORA-01790: expression must have same datatype as corresponding expression
  File "django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
  File "django/db/backends/oracle/base.py", line 510, in execute
    return self.cursor.execute(query, self._param_generator(params))

DatabaseError: ORA-01790: expression must have same datatype as corresponding expression
(10 additional frame(s) were not displayed)
...
  File "job_queue/management/commands/worker.py", line 48, in __call__
    return execute(sql, params, many, context)
  File "django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
  File "django/db/utils.py", line 89, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
  File "django/db/backends/oracle/base.py", line 510, in execute
    return self.cursor.execute(query, self._param_generator(params))

Adding TextField: TO_CLOB mapping to the following object seems to fix the issue: ​https://github.com/django/django/blob/c4e2fc5d9872c9a0c9c052a2e124f8a9b87de9b4/django/db/backends/oracle/utils.py#L34

I am planning to open a PR with the fix if this is an acceptable solution.