Support reading EO-SIP LAC data

[mraspaud]

This PR adds support for the EO-SIP LAC formats.

In particular, the EBCDIC decoding for dataset names is implemented, and the fixed header type for POD data is added as an option.

[codecov]

Codecov Report

Attention: Patch coverage is 98.65772% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 77.04%. Comparing base (cbf2d7c) to head (2753057).
Report is 1 commits behind head on main.

Files	Patch %	Lines
pygac/pod_reader.py	88.88%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #125      +/-   ##
==========================================
+ Coverage   74.39%   77.04%   +2.64%     
==========================================
  Files          32       32              
  Lines        2882     3001     +119     
==========================================
+ Hits         2144     2312     +168     
+ Misses        738      689      -49     

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[sfinkens]

Nice work! I had a couple inline refactoring ideas and two thoughts:

1. I wonder what happens if PODReader.can_read (inherited from Reader) calls PODReader.read_header without the eosip_header argument. Would that work with EOSIP files?
2. Would it make sense to make the signature format agnostic?

read_header(..., header="auto")  # determine based on timestamp
read_header(..., header=header3)  # use exactly this header

[mraspaud]

Nice work! I had a couple inline refactoring ideas and two thoughts:

1. I wonder what happens if `PODReader.can_read` (inherited from `Reader`) calls `PODReader.read_header` without the `eosip_header` argument. Would that work with EOSIP files?

Yes, that is not a problem since the header isn't used for anything in that function, just check that is doesn't raise any errors...

2. Would it make sense to make the signature format agnostic?

read_header(..., header="auto")  # determine based on timestamp
read_header(..., header=header3)  # use exactly this header

That would be really nice, however how will satpy know what pygac header to use?

[sfinkens]

how will satpy know what pygac header to use?

Good point... I tried, but I'm not sure this is better...

pygac:
EOSIP_HEADER = header3.copy()

satpy:
from pygac import EOSIP_HEADER
reader_kwargs["header"] = EOSIP_HEADER

[mraspaud]

I just thought while cycling home that we could instead pass the header timstamp?
eg

read_header(..., header_timestamp="auto")  # for automatic, current behaviour, default
read_header(..., header_timestamp=datetime(2000, 1, 1))  # to choose a specific one

or is this too obscure?

how will satpy know what pygac header to use?

Good point... I tried, but I'm not sure this is better...

pygac:
EOSIP_HEADER = header3.copy()

satpy:
from pygac import EOSIP_HEADER
reader_kwargs["header"] = EOSIP_HEADER

[sfinkens]

I like that!

[sfinkens]

Awesome, thanks for adding a test with a real file! There are some codefactor warnings (E241), otherwise looks good to me. 👍