Update Debian/Ubuntu package signing key location to /etc/apt/keyrings for improved security

[Copilot]

Updates the APT package signing key storage location from /etc/apt/trusted.gpg.d/ to /etc/apt/keyrings/ across all InfluxData installation documentation to follow modern security best practices.

Background

The current documentation instructs users to store GPG keys in /etc/apt/trusted.gpg.d/, which creates globally trusted keys for all repositories. This approach is less secure because these keys are trusted system-wide and cannot be restricted to specific repositories.

The modern recommended approach uses /etc/apt/keyrings/ with the signed-by option in sources lists, providing better security isolation by allowing per-repository key assignment rather than global trust.

Changes Made

Updated installation instructions in 5 documentation files:

• Telegraf v1 installation (content/telegraf/v1/install.md) - Both Ubuntu 20.04+ and legacy versions
• InfluxDB v1 installation (content/influxdb/v1/introduction/install.md) - Both installation methods
• InfluxDB v2 installation (content/influxdb/v2/install/_index.md) - Ubuntu/Debian section
• InfluxDB 3 Clustered CLI (content/influxdb3/clustered/reference/cli/influxctl/_index.md)
• InfluxDB 3 Cloud Dedicated CLI (content/influxdb3/cloud-dedicated/reference/cli/influxctl/_index.md)

Technical Details

The changes replace:

sudo tee /etc/apt/trusted.gpg.d/influxdata-archive.gpg
echo 'deb [signed-by=/etc/apt/trusted.gpg.d/influxdata-archive.gpg] ...'

With:

sudo tee /etc/apt/keyrings/influxdata-archive.gpg  
echo 'deb [signed-by=/etc/apt/keyrings/influxdata-archive.gpg] ...'

This maintains full backward compatibility while improving security isolation. The /etc/apt/keyrings/ directory is supported in apt 2.4+ (Ubuntu 22.04+, Debian 12+), and the existing signed-by configuration ensures proper per-repository key assignment.

Fixes #6297.

Warning

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[jstirnaman]

@jdstrand Should we remove the use of archive_compat.gpg here?

[jdstrand]

This is in the <!------------------------BEGIN OLDER THAN UBUNTU 20.04 LTS---------------------> section, so use of archive_compat.gpg is correct there. So leave it if you still want docs for older releases, otherwise remove the whole section.