Improve sponsor handling #1020

Job	Run time
Build docs & run doctests	27s
Verify dev env (ubuntu-latest)	29s
Run CodSpeed benchmarks	2m 38s
Verify dev env (windows-latest)	1m 10s
Check types using pyright	25s
Tests & Mypy on 3.7	1m 0s
Tests & Mypy on 3.8	31s
Tests & Mypy on 3.9	51s
Tests & Mypy on 3.10	1m 7s
Tests & Mypy on 3.11	1m 1s
Tests & Mypy on 3.12	1m 18s
Tests & Mypy on 3.13	48s
Tests & Mypy on pypy-3.8	1m 23s
Tests & Mypy on pypy-3.9	51s
Tests & Mypy on pypy-3.10	56s
Combine & check coverage.	12s
required-checks-pass	2s
	15m 9s

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