add supprt for the custom auth plugin

[firefart]

This PR adds support for the CustomAuth plugin. When it's enabled the header is defined in the nginx config so it's passed though to php-fpm and the plugin is configured using the new environment variables.
This comes in handy when you run misp behind an authenticating reverse proxy

[Copilot]

Pull request overview

This PR adds support for the CustomAuth plugin to enable authentication via custom HTTP headers, typically when MISP is deployed behind an authenticating reverse proxy. The implementation includes environment variable configuration, Docker Compose integration, nginx configuration to pass the custom header to PHP-FPM, and MISP plugin configuration through the setup scripts.

Note: The PR title contains a spelling error: "supprt" should be "support".

Changes:

• Added CustomAuth plugin environment variables to template.env and docker-compose.yml
• Implemented nginx configuration to forward custom authentication headers to PHP-FPM
• Added set_up_custom_auth function to configure the MISP CustomAuth plugin settings
• Updated README with CustomAuth documentation and usage examples

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
template.env	Added commented configuration variables for CustomAuth plugin settings
docker-compose.yml	Added CustomAuth environment variables to misp-core service
core/files/entrypoint_nginx.sh	Added nginx initialization logic to configure FastCGI parameter for custom auth header; removed trailing whitespace
core/files/configure_misp.sh	Added set_up_custom_auth function to enable/disable and configure the CustomAuth plugin in MISP
README.md	Added CustomAuth documentation section; fixed JSON and list formatting; removed trailing whitespace

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

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