feat: migrate Slack management pages to React (#231) #268

Job	Run time
test (api, api)	21s
test (integrations-slack-gateway, integrations/slack-gateway)	17s
test (operator, operator)	18s
test (acptext, integrations/acptext)	14s
docker-build (api, api/Dockerfile)	1m 19s
docker-build (integrations-slack-gateway, integrations/slack-gateway/Dockerfile)	22s
test (integrations-github-app, integrations/github-app)	22s
	3m 13s

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