chore(api)!: Model .fromJson() Refactor #2689

Job	Run time
test / test-dart-vm (3.3.0)	2m 13s
test / test-dart-vm (stable)	2m 34s
ddc_test / test-dart-ddc (3.3.0, chrome)	3m 40s
ddc_test / test-dart-ddc (3.3.0, firefox)	3m 48s
ddc_test / test-dart-ddc (stable, chrome)	3m 53s
dart2js_test / test-dart-2js (3.3.0, chrome)	4m 12s
ddc_test / test-dart-ddc (stable, firefox)	4m 3s
dart2js_test / test-dart-2js (3.3.0, firefox)	4m 12s
native_test / test-dart-native (macos-latest)	3m 13s
dart2js_test / test-dart-2js (stable, chrome)	4m 7s
native_test / test-dart-native (windows-latest)	3m 24s
dart2js_test / test-dart-2js (stable, firefox)	4m 23s
	43m 42s

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