Ottu-py

- Added option to set `timeout` on all requests made by the SDK.

- Added option to send dynamic parameters to the Checkout API. The affected methods are:
- `Ottu.checkout(...)`
- `Ottu.checkout_autoflow(...)` (via `checkout_extra_args` parameter)
- `Ottu.auto_debit_autoflow(...)` (via `checkout_extra_args` parameter)
- A new parameter `include_sdk_setup_preload` added new parameter to the Checkout API
- Removed positional arguments from following methods:
- `Ottu.checkout(...)`
- `Ottu.Session.update(...)`
- `Ottu.checkout_autoflow(...)`
- `Ottu.auto_debit_autoflow(...)`

- Remove irrelevant `customer_id` check from checkout API
- Loosen `httpx` dependency (now supports `httpx>=0.25.0`)

- Set default value of `operation` parameter to `None` in `Ottu.get_payment_methods(...)` method (Earlier it was `"purchase"`).
- Removed following Django settings in favor of [`OTTU_AUTH`](/README.mdauthentication-settings)
- `OTTU_AUTH_USERNAME`
- `OTTU_AUTH_PASSWORD`
- `OTTU_AUTH_API_KEY`

- Updated `Django` dependency to `<4.3` to fix compatibility issues.

Added
- New authentication classes (`KeycloakPasswordAuth` and `KeycloakClientAuth`).
- New method `Ottu.get_payment_methods(...)` to get available payment methods.