tedge flows handles mapper specific built-in functions

[reubenmiller]

Is your refactoring request related to a problem? Please describe.

Since tedge-mapper-c8y now uses flows to provide the cloud mappings, it would be useful for users to be able to test out mapping using the tedge flows test and tedge flows list cli commands.

Describe the solution you'd like

Depending on the time available, either one of the options is to be implemented:

• Option 1: Print out a warning that Cumulocity mapper specific built-in functions aren't available to be tested via the tedge flows test command

• Option 2: Support loading the built-in mapper specific commands

Describe alternatives you've considered

Additional context

[reubenmiller]

The tedge flows list command also needs to know about the mapper specific built-in functions, otherwise it results in errors when trying to list flows for the c8y mapper:

$ tedge flows list --mapper c8y
2026-02-25T14:00:53.794491Z ERROR flows: Failed to compile flow /opt/homebrew/etc/tedge/mappers/c8y/flows/measurements.toml: Builtin transformer not found: cache-early-messages
2026-02-25T14:00:53.795162Z ERROR flows: Failed to compile flow /opt/homebrew/etc/tedge/mappers/c8y/flows/alarms.toml: Builtin transformer not found: cache-early-messages
2026-02-25T14:00:53.795177Z ERROR flows: Failed to compile flow /opt/homebrew/etc/tedge/mappers/c8y/flows/events.toml: Builtin transformer not found: cache-early-messages
2026-02-25T14:00:53.795188Z ERROR flows: Failed to compile flow /opt/homebrew/etc/tedge/mappers/c8y/flows/health.toml: Builtin transformer not found: cache-early-messages
Flow        : flow.toml (unversioned)
Description : none
File        : /opt/homebrew/etc/tedge/mappers/c8y/flows/certificate-alert/flow.toml
Step 1      : /opt/homebrew/etc/tedge/mappers/c8y/flows/certificate-alert/dist/main.js

Flow        : units.toml (unversioned)
Description : none
File        : /opt/homebrew/etc/tedge/mappers/c8y/flows/units.toml
Step 1      : update-context