SsmBaseSettings is always case-sensitive

[keith-at-coastal]

There appears to be a bug that prevents reading case-insensitive settings from the environment or a .env file. Here is a minimal example of the issue:

from pydantic_ssm_settings import SsmBaseSettings
from pydantic import ValidationError
from os import environ


class SimpleSettings(SsmBaseSettings):
    foo: str


# can read parameters from the environment if the case matches
environ['foo'] = 'foo'
s = SimpleSettings()
assert s.foo == 'foo'
print('Loaded just fine, as expected')
del environ['foo']

# can't read parameters from the environment if the case does not match
environ['FOO'] = 'foo'
try: 
    s = SimpleSettings()
except ValidationError:
    print('Failed to load with upper case variable names')
del environ['FOO']

# can't explicitly set the case sensitivity 
environ['FOO'] = 'foo'
try:
    s = SimpleSettings(_case_sensitive=False)
except TypeError as err:
    assert "multiple values for argument '_case_sensitive'" in str(err)
    print('Failed to force case insensitive') 

I tracked the problem down to an incorrect call to super().__init__():

pydantic-ssm-settings/pydantic_ssm_settings/settings.py

Line 51 in 9a079c8

super().__init__(self, *args, **kwargs)

The current call is super().__inti__(self, *args, **kwargs), but is should not include self. The result of this bug is that self gets passed along as the _case_sensitive argument. It is "truthy" so we end up with a case sensitive settings class, and because it is already provided, we cannot override it.

I think the fix is as simple as deleting the offending self.

[keith-at-coastal]

This PR should do the trick: #17