minor improvements in server.ts: instantiate CommonEngine only once at module load

[saschaszott]

References

n/a

Description

This PR contains a minor improvement in server.ts. It instantiates CommonEngine only once at module load instead of on every SSR render. This is possible as Its config is already final by the time requests are served and never changes at runtime.

Instructions for Reviewers

Both changes do not change the current behavior.

Verify SSR rendering still works for a normal item landing page request when running app in production mode.

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[tdonohue]

NOTE: This PR and #6360 partially overlap. We'll want to determine which to move forward or if we should combine them in some way. See also my comments at #6360 (comment)

[github-actions]

Hi @saschaszott,
Conflicts have been detected against the base branch.
Please resolve these conflicts as soon as you can. Thanks!

[tdonohue]

@saschaszott : Please rebase this, as I just merged #6360 (so you can just remove your changes to the caching regex as it's now removed). Once this is rebased, I can gladly review/test this quickly.

[saschaszott]

@tdonohue , I've resolved the merge conflict and updated PR title and description.