useas: configmap may result in invalid bash variable names

[starpit]

e.g. if my dataset is test7-data, then you generate env vars like test7-data_bucket, which is not a valid bash variable name. 🤔

i'm not sure quite what the best fix is here. maybe changing dashes and any other invalid bash variable names to underscore? i think the valid character class is [a-zA-z0-9_]+, and to be safe, perhaps avoid starting with a digit, [a-zA-Z_][a-zA-Z0-9_]*. i think this is known as a C_IDENTIFIER.