Add throttling to contact api endpoint #1252

Job	Run time
Test dev setup on ubuntu-latest	27s
Build python wheel	1m 9s
Test dev setup on windows-latest	1m 16s
Test dev setup on macos-latest	22s
lint / Lint	15s
Test (Python: 3.8, DB: mysql)	28m 27s
End-to-end Test (Python: 3.12, DB: postgres)	6m 16s
Test installation of all dependencies	48s
Test (Python: 3.8, DB: postgres)	26m 59s
Test (Python: 3.12, DB: mysql)	31m 27s
Test (Python: 3.12, DB: postgres)	30m 21s
Indicate completion to coveralls	4s
required-checks-pass	4s
	2h 7m 55s

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