[Gateway Docs] Replace References to AppGateServer with PATH

[red-0ne]

Summary

• Update all Gateway AppGateServer references with PATH
• Adapt documentation to suit PATH workflow.

Issue

AppGateServer must be deprecated and replaced by the PATH Gateway

Type of change

Select one or more from the following:

• New feature, functionality or library
• Consensus breaking; add the consensus-breaking label if so. See [Infra] Automatically add the consensus-breaking label #791 for details
• Bug fix
• Code health or cleanup
• Documentation
• Other (specify)

Testing

• Documentation: make docusaurus_start; only needed if you make doc changes

Sanity Checklist

• I have tested my changes using the available tooling
• I have commented my code
• I have performed a self-review of my own code; both comments & source code
• I create and reference any new tickets, if applicable
• I have left TODOs throughout the codebase, if applicable

[Olshansk]

@red-0ne A few minor NITs + we need a response from @okdas on this:

Should be g2g after.

[gitguardian]

⚠️ GitGuardian has uncovered 3 secrets following the scan of your pull request.

Please consider investigating the findings and remediating the incidents. Failure to do so may lead to compromising the associated services or software components.

🔎 Detected hardcoded secrets in your pull request

GitGuardian id	GitGuardian status	Secret	Commit	Filename
14150880	Triggered	Generic High Entropy Secret	5ebee56	localnet/kubernetes/config-path-3.yaml	View secret
14150881	Triggered	Generic High Entropy Secret	5ebee56	localnet/kubernetes/config-path-2.yaml	View secret
13506804	Triggered	Generic High Entropy Secret	5ebee56	localnet/kubernetes/config-path-1.yaml	View secret

🛠 Guidelines to remediate hardcoded secrets

1. Understand the implications of revoking this secret by investigating where it is used in your code.
2. Replace and store your secrets safely. Learn here the best practices.
3. Revoke and rotate these secrets.
4. If possible, rewrite git history. Rewriting git history is not a trivial act. You might completely break other contributing developers' workflow and you risk accidentally deleting legitimate data.

To avoid such incidents in the future consider

• following these best practices for managing and storing secrets including API keys and other credentials
• install secret detection on pre-commit to catch secret before it leaves your machine and ease remediation.

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^{🦉 GitGuardian detects secrets in your source code to help developers and security teams secure the modern development process. You are seeing this because you or someone else with access to this repository has authorized GitGuardian to scan your pull request.}

[Olshansk]

Let's merge it in!