SQC-646 Implement DatabaseServer service for Hyperdrive binding

[Ltadrian]

Implement DatabaseServer service to handle use case of upgrading client connection to TLS stream over TCP to databases that require SSL.

This is useful for local development with Hyperdrive binding where running wrangler dev can not automatically connect to an external database fails upgrading to TLS stream.

• Handles custom TLS start up packets for postgres/mysql
• Handles sslmodes 'prefer' anad 'require'
• Implement unit tests for DatabaseServer service with Hyperdrive binding
• Tested locally against local databases/external databases (i.e neondb/planetscale)

[github-actions]

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[Ltadrian]

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[Ltadrian]

I have read the CLA Document and I hereby sign the CLA

[Ltadrian]

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[kentonv]

Please come talk to us about what you're trying to do here.

This PR is introducing a major new public-facing feature to the workerd architecture. This sort of thing can't just arrive as a PR, it needs docs explaining what it is and why it is needed and some sort of discussion with the code owners first.

In particular I don't understand why ExternalServer is insufficient here. It's already intended to support arbitrary TCP connections. Why are databases special?

[ReppCodes]

Please come talk to us about what you're trying to do here.

This PR is introducing a major new public-facing feature to the workerd architecture. This sort of thing can't just arrive as a PR, it needs docs explaining what it is and why it is needed and some sort of discussion with the code owners first.

In particular I don't understand why ExternalServer is insufficient here. It's already intended to support arbitrary TCP connections. Why are databases special?

We have talked to you and Dan repeatedly, and demo'd this a couple weeks ago.

[Ltadrian]

@kentonv I responded in the internal google chat thread!