Unclear Regex-Based error message when editing environment variable name via JSON in Azure Container Apps

[v-ruizh]

OS: Win 11
Build Version: 20260107.1

Repro Steps:

1. Use "Edit Container App (Advanced)..." to open the container app's JSON configuration.
2. Change an environment variable name to an invalid format "123".
3. Save and deploy the changes.
4. Check whether the error message is clear or not.

Expect:
The error message clearly explains the naming rules.

Actual:
The error message displays a raw regex string.

More Info:
This issue does not reproduce in "Edit Environment Variable Name" option.

[motm32]

This message was copied from the portal but we can probably make it easier to read. The portal may have also changed the message by now.