Allow substitution of unsupported characters in tags with alternative character.

[skrausedxccom]

according the documentation, Forward-Slash can be used for AWS/EC2 metrics. But AWS EC2 tagging does not allow foward slash.

[knizami]

Hello, thanks for creating this issue. I believe forward slashes are allowed unless tag retrieval via instance metadata is being used:
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/Using_Tags.html#work-with-tags-in-IMDS

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/Using_Tags.html#tag-restrictions

I have updated the issue so that the solution will allow you to provide a dictionary for character substitutions. For example, provided a dictionary:

substitution_map = { '@': '\' }

The solution will create the alarm substituting the '@' sign found in the tag with a '' before processing the tag: