Prevent save data in apl when data already exists

[poulch]

No description provided.

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Latest commit: bd23bca

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[github-actions]

Package	Line Rate	Branch Rate	Complexity	Health
src	79%	93%	0	✔
src.APL	85%	85%	0	✔
src.APL.saleor-cloud	75%	86%	0	✔
src.APL.vercel-kv	54%	69%	0	➖
src.app-bridge	88%	86%	0	✔
src.handlers.next	89%	83%	0	✔
src.handlers.next.saleor-webhooks	94%	80%	0	✔
src.middleware	60%	97%	0	➖
src.settings-manager	96%	89%	0	✔
src.test-utils	100%	90%	0	✔
src.util	82%	100%	0	✔
Summary	83% (3842 / 4616)	86% (455 / 526)	0	✔

[lkostrowski]

1. this will prevent all installations except first to work, because APL is not pruned after app is uninstalled
2. overwriting APL is something we want
3. users can't install 2 apps with the same id, so this case should not happen (except old installations)