feat: export with fixed-api-key

[dajianguo]

Summary

A fixed api-key keeps the api-key of app services unchanged when we import, export or upgrade the dsl.

Resolves #10632
Resolves #9559

Screenshots

test-app-apikey:	test-app-apikey:	test-dataset-appkey:	test-pk-check:	test-api:	test-api:

Checklist

Important

Please review the checklist below before submitting your pull request.

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

[laipz8200]

I don’t recommend doing this, as allowing custom keys is more likely to lead to security issues due to negligence.

[dajianguo]

I don’t recommend doing this, as allowing custom keys is more likely to lead to security issues due to negligence.

Add verification, the key length must not be less than 20 bits？

We use dify as the backend service, which is deployed in the intranet and is not open to the public, so it is relatively safe.