feat: create a Rust sample plugin for HMAC cookie authorization.

[walves-cit]

This plugin is a HMAC cookie authorization showcase.

Technically, this is performed by ensuring that the request has a valid HMAC cookie.

This examples contains only a Rust version.

[snippet-bot]

Here is the summary of changes.

You are about to add 1 region tag.

• plugins/samples/hmac_authcookie/plugin.rs:15, tag serviceextensions_plugin_hmac_authcookie

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