Add generic calibration coefficient selector

[sfinkens]

As a first step towards channel-specific calibration modes (#2599), I added a generic calibration coefficient selector that can be used by all readers.

Example: Three sets of coefficients are available (nominal, meirink, gsics). A user wants to calibrate

• channel 1 with “meirink”
• channels 2/3 with “gsics”
• channel 4 with custom coefficients
• remaining channels with default (nominal) coefficients

The user would provide a wishlist via reader_kwargs:

calib_wishlist = {
    "ch1": "meirink",
    ("ch2", "ch3"): "gsics"
    "ch4": {"mygain": 123},
}
# Also possible: Same mode for all channels via
# calib_wishlist = "gsics"

Readers would compile a dictionary of coefficients

coefs = {
    "nominal": {
        "ch1": 1.0,
        "ch2": 2.0,
        "ch3": 3.0,
        "ch4": 4.0,
        "ch5": 5.0,
    },
    "meirink": {
        "ch1": 1.1,
    },
    "gsics": {
        "ch2": 2.2,
        # ch3 coefficients are missing
    }
}

and could then make queries to get the desired coefficients:

>>> from satpy.readers.utils import CalibrationCoefficientPicker
>>> picker = CalibrationCoefficientPicker(coefs, calib_wishlist)
>>> picker.get_coefs("ch1")
{"coefs": 1.0, "mode": "meirink"}
>>> picker.get_coefs("ch2")
{"coefs": 2.2, "mode": "gsics"}
>>> picker.get_coefs("ch3")
KeyError: 'No gsics calibration coefficients for ch3'
>>> picker.get_coefs("ch4")
{"coefs": {"mygain": 123}, "mode": "external"}
>>> picker.get_coefs("ch5")
{"coefs": 5.0, "mode": "nominal"}

Fallback to nominal coefficients for channel 3:

>>> picker = CalibrationCoefficientPicker(coefs, calib_wishlist, fallback="nominal")
>>> picker.get_coefs("ch3")
WARNING No gsics calibration coefficients for ch3. Falling back to nominal.
{"coefs": 3.0, "mode": "nominal"}

Let me know what you think!

• Tests added
• Fully documented

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.94%. Comparing base (ab55c4a) to head (417c768).
Report is 127 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2811      +/-   ##
==========================================
+ Coverage   95.91%   95.94%   +0.02%     
==========================================
  Files         366      366              
  Lines       53504    53613     +109     
==========================================
+ Hits        51321    51441     +120     
+ Misses       2183     2172      -11     

Flag	Coverage Δ
behaviourtests	4.04% <0.00%> (-0.01%)	⬇️
unittests	96.04% <100.00%> (+0.02%)	⬆️

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[coveralls]

Pull Request Test Coverage Report for Build 9483973148

Details

• 71 of 71 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.005%) to 96.045%

---

Totals
Change from base Build 9418285216:	0.005%
Covered Lines:	51632
Relevant Lines:	53758

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9485685926

Details

• 59 of 59 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.004%) to 96.044%

---

Totals
Change from base Build 9418285216:	0.004%
Covered Lines:	51620
Relevant Lines:	53746

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9495737646

Details

• 60 of 60 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.004%) to 96.044%

---

Totals
Change from base Build 9418285216:	0.004%
Covered Lines:	51621
Relevant Lines:	53747

---

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[coveralls]

Pull Request Test Coverage Report for Build 9499819988

Warning: This coverage report may be inaccurate.

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Details

• 104 of 104 (100.0%) changed or added relevant lines in 2 files are covered.
• 42 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.008%) to 96.048%

---

Files with Coverage Reduction	New Missed Lines	%
satpy/resample.py	42	88.74%

Totals
Change from base Build 9418285216:	0.008%
Covered Lines:	51665
Relevant Lines:	53791

---

💛 - Coveralls

[mraspaud]

Looks great! just a couple of minor suggestions

[sfinkens]

I also renamed "selector" to "picker"

[coveralls]

Pull Request Test Coverage Report for Build 9512668046

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

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Details

• 106 of 106 (100.0%) changed or added relevant lines in 2 files are covered.
• 42 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.008%) to 96.048%

---

Files with Coverage Reduction	New Missed Lines	%
satpy/resample.py	42	88.74%

Totals
Change from base Build 9418285216:	0.008%
Covered Lines:	51667
Relevant Lines:	53793

---

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[coveralls]

Pull Request Test Coverage Report for Build 9513296644

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 109 of 109 (100.0%) changed or added relevant lines in 2 files are covered.
• 42 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.008%) to 96.048%

---

Files with Coverage Reduction	New Missed Lines	%
satpy/resample.py	42	88.74%

Totals
Change from base Build 9418285216:	0.008%
Covered Lines:	51670
Relevant Lines:	53796

---

💛 - Coveralls

[mraspaud]

Great job, lgtm!