Prototype implementation for private access poc

[stradig]

Problem

For the Private Access POC we want users to be able to disable access from the public proxy. To limit the number of changes this can be done by configuring an IP allowlist [ "255.255.255.255" ]. For the Private Access proxy a new commandline flag allows to disable IP allowlist completely.

See https://www.notion.so/neondatabase/Neon-Private-Access-POC-Proposal-8f707754e1ab4190ad5709da7832f020?d=887495c15e884aa4973f973a8a0a582a#7ac6ec249b524a74adbeddc4b84b8f5f for details about the POC.,

Summary of changes

• Adding the commandline flag is_private_access_proxy=true will disable IP allowlist

[orca-security-us]

Orca Security Scan Summary

Status	Check	Issues by priority
Passed	Infrastructure as Code	0   0   0   0	View in Orca
Passed	Secrets	0   0   0   0	View in Orca
Passed	Vulnerabilities	0   0   0   0	View in Orca

[github-actions]

3857 tests run: 3743 passed, 0 failed, 114 skipped (full report)

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Flaky tests (5)

Postgres 15

• test_ondemand_wal_download_in_replication_slot_funcs: release-x86-64
• test_subscriber_restart: release-x86-64

Postgres 14

• test_subscriber_restart: release-x86-64
• test_wal_restore_initdb: release-x86-64
• test_wal_restore: release-x86-64

Code coverage* (full report)

• functions: 31.7% (7354 of 23183 functions)
• lines: 50.0% (59558 of 119169 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
638b856 at 2024-09-12T11:27:20.788Z :recycle:}