Proposed changes

Fix the tedge's linux package dependency to mosquitto by making it a weak dependency so that mosquitto is not installed by default when installing tedge directly (and not via the tedge-full or tedge-minimal virtual linux packages).

This will allow users to install tedge and any other package which depends on tedge (like tedge-agent) to be installed without mosquitto. The virtual packages will have a hard dependency to mosquitto as this is a "typical" setup and mosquitti is required on the main device.

The official thin-edge.io/install.sh script uses the virtual packages, so this does not break and existing behaviour.

FYI: Debian has good documentation which go into details about the package dependency types.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (general improvements like code refactoring that doesn't explicitly fix a bug or add any new functionality)
• Documentation Update (if none of the other choices apply)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Paste Link to the issue

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA (in all commits with git commit -s)
• I ran cargo fmt as mentioned in CODING_GUIDELINES
• I used cargo clippy as mentioned in CODING_GUIDELINES
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments