feat: standardise RGBN imagery TDE-693

[rebclarke]

Motivation

As a remote sensing scientist I want RGBNIR + Alpha TIFFs available in a public bucket so that I don’t need to request data from several different councils and/or LINZ.

This requires handling RGBN which can be in the following forms:

• R,G,B,Undefined - where the band labelled Undefined is NIR.
• R,G,B,Alpha - where the band labelled Alpha is NIR.
• R,G,B,Undefined,Alpha - where the band labelled Undefined is NIR and Alpha is Alpha.

The desired output bands are:
R/G/B/NIR/A 5-band TIFFs

Modifications

Added a new preset rgbnir_zstd
Updated bands checks to handle RGBNIR scenarios
Updated footprint creation to handle RGBNIR
Unit tests and doctests
End-to-end test for RGBNIR

Verification

PR container, unit tests, end-to-end tests.

[paulfouquet]

Have you considered extracting the logic of the different steps into individual helper functions?
As an example, you could look at having the following functions

1. get_alpha_and_nir_args()
2. get_gray_band_args()
3. get_palette_band_args()
4. get_rgb_bands_args()

that would be called in that main function.

I think it would improve unit testing, maintainability and readability of this function.