Avoid multiple assignments of constant ALLOWED_INPUT_SCHEMAS

[candleindark]

This PR avoids multiple assignment of the constant ALLOWED_INPUT_SCHEMAS. Incidentally, it improves readability, and ensures ALLOWED_VALIDATION_SCHEMAS is always sorted.

Please, also checkout an alternative to this PR posted below.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.29%. Comparing base (6fd04fb) to head (c44d1f3).
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Flag	BASE (6fd04fb)	HEAD (c44d1f3)
unittests	528	24

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@@            Coverage Diff             @@
##           master     #280      +/-   ##
==========================================
- Coverage   97.54%   92.29%   -5.26%     
==========================================
  Files          16       16              
  Lines        1753     1751       -2     
==========================================
- Hits         1710     1616      -94     
- Misses         43      135      +92     

Flag	Coverage Δ
unittests	92.29% <100.00%> (-5.26%)	⬇️

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[candleindark]

If set(ALLOWED_TARGET_SCHEMAS) is always a subset of set(ALLOWED_INPUT_SCHEMAS), as it currently is, we can further simplify the definition of ALLOWED_VALIDATION_SCHEMAS to the following.

Suggested change

	ALLOWED_VALIDATION_SCHEMAS = sorted(
	set(ALLOWED_INPUT_SCHEMAS).union(ALLOWED_TARGET_SCHEMAS)
	)
	ALLOWED_VALIDATION_SCHEMAS = ALLOWED_INPUT_SCHEMAS

[yarikoptic]

feels like indeed we could have simplified like this, but for now let's just keep as is, may be there would be some time some divergence ;-)