Add DayOfWeek ToSchema instance. #56

Job	Run time
build and test (stack) (ubuntu-latest)	10m 50s
build and test (stack) (macOS-latest)	22m 41s
build and test (cabal) (8.6.5, 3.10.2.0, ubuntu-latest)	8m 15s
build and test (cabal) (8.6.5, 3.10.2.0, macOS-latest)	18m 37s
build and test (cabal) (8.8.4, 3.10.2.0, ubuntu-latest)	7m 46s
build and test (cabal) (8.8.4, 3.10.2.0, macOS-latest)	17m 13s
build and test (cabal) (8.10.7, 3.10.2.0, ubuntu-latest)	7m 54s
build and test (cabal) (8.10.7, 3.10.2.0, macOS-latest)	16m 2s
build and test (cabal) (9.0.2, 3.10.2.0, ubuntu-latest)	8m 20s
build and test (cabal) (9.0.2, 3.10.2.0, macOS-latest)	13m 42s
build and test (cabal) (9.2.8, 3.10.2.0, ubuntu-latest)	7m 45s
build and test (cabal) (9.2.8, 3.10.2.0, macOS-latest)	15m 49s
build and test (cabal) (9.4.8, 3.10.2.0, ubuntu-latest)	7m 59s
build and test (cabal) (9.4.8, 3.10.2.0, macOS-latest)	15m 34s
build and test (cabal) (9.6.4, 3.10.2.0, ubuntu-latest)	6m 50s
build and test (cabal) (9.6.4, 3.10.2.0, macOS-latest)	12m 14s
build and test (cabal) (9.8.1, 3.10.2.0, ubuntu-latest)	6m 32s
build and test (cabal) (9.8.1, 3.10.2.0, macOS-latest)	14m 45s
	3h 38m 48s

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