Pocketsmith-api

Added
- Added missing `currency_code` field to `BudgetAnalysis` and `Period` types (see [GH6](https://github.com/theY4Kman/python-pocketsmith-api/pull/6), thanks [brett-comber](https://github.com/brett-comber))

Changed
- User-Agent reported by client changed to `python-pocketsmith/<version>` (previously was `OpenAPI-Generator/<version>/python`)

Fixed
- `budgeting.get_trend_analysis()` now returns proper response data (see [GH6](https://github.com/theY4Kman/python-pocketsmith-api/pull/6), thanks [brett-comber](https://github.com/brett-comber))
- Corrected typo in `refund_amount`, was previously `refund_amound` (see [GH6](https://github.com/theY4Kman/python-pocketsmith-api/pull/6), thanks [brett-comber](https://github.com/brett-comber))
- `__version__` now correctly reported from `pocketsmith` package (see [GH6](https://github.com/theY4Kman/python-pocketsmith-api/pull/6), thanks [brett-comber](https://github.com/brett-comber))

Added
- Expose overlooked `attachments` and `category_rules` API clients on `PocketsmithClient` (see [GH4](https://github.com/theY4Kman/python-pocketsmith-api/pull/4), thanks [brett-comber](https://github.com/brett-comber))

Fixed
- Include required `certifi` dependency when installing

Changed
- Remove support for Python 2.7 — support only given for 3.6+

Fixed
- Resolved various nullable fields not being marked nullable (addressing further validation errors in strict generated API clients)

Fixed
- Allow Data Feeds Connection/Account/Provider IDs to be strings or integers (addresses validation errors in generated API clients)