[BUG]: CHIRPS Rainfall Data not working for all partial data types

[rowannicholls]

Describe the bug Processing the geospatial/chirps-rainfall data using monthly data does not work.

To Reproduce Steps to reproduce the behaviour:

1. Clone the repo, set up the venv, install the dart-pipeline
2. Run the following to get the required data:

• uv run dart-pipeline get meteorological/chirps-rainfall year=2023
• uv run dart-pipeline get meteorological/chirps-rainfall year=2023 month=5
• uv run dart-pipeline get geospatial/gadm iso3=VNM

These will either complete or skip (if the data has already been downloaded).

3. Run the following to process the data:

• uv run dart-pipeline process geospatial/chirps-rainfall iso3=VNM partial_date=2023
• uv run dart-pipeline process geospatial/chirps-rainfall iso3=VNM partial_date=2023-05

The first will work but the second will fail with error FileNotFoundError: CHIRPS rainfall data not found for: 2023-05

Expected behavior The processing sub-pipeline should work in producing a CSV for Vietnam rainfall for May 2023.

Screenshots N/A

Environment (please complete the following information):

• DART pipeline: geospatial/chirps-rainfall
• OS: macOS Sonoma

Additional context N/A