use a singleton http agent for queue events + Reduce metrics cardinality

[fenos]

What kind of change does this PR introduce?

Bug fix

What is the current behavior?

• Everytime a queue message calls createStorage each storage client uses a different HTTP pool agent not taking advantage of keep-alive

• All metrics requires the tenant_id label, which creates high cardinality metrics

What is the new behavior?

• All events are now sharing a single HTTP agent pool
• reduce metrics cardinality by removing the tenant_id label

[coveralls]

Pull Request Test Coverage Report for Build 6721048154

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• 79 of 80 (98.75%) changed or added relevant lines in 9 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.04%) to 84.0%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/database/connection.ts	1	2	50.0%

Totals
Change from base Build 6618123878:	0.04%
Covered Lines:	7508
Relevant Lines:	8866

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💛 - Coveralls

[github-actions]

🎉 This PR is included in version 0.43.9 🎉

The release is available on GitHub release

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