Capture `${...}` pattern less strict to throw explicitly

[mohoff]

In the hydrate config step, we use src/utils/substitute-with-env.ts to substitute string patterns like ${<VAR>} with process.env[<VAR>] in case it's not nil. We can improve the user experience here and catch invalid formats of <VAR>.

Examples:

• In case we find $VAR (no curly braces), we can at least warn the user that there might be a wrong format.
• In case we find ${}, we can at least warn that the user probably entered a wrong value.
• In case we find ${1ABC} or ${A-BC}, we can at least warn since both are invalid.

More technical context:

Currently, we capture for /\${(\w+)}/g (1), which substitutes 1+ word characters. Instead we can capture for a less strict /\${(.*)}/g so that we can explicitly throw when a matched group doesn't suffice constraints of valid env var names, which are /[a-zA-Z_]+[a-zA-Z0-9_]*/ (2)

This improves the usability in a way that users are made aware of potentially invalid template strings, e.g. $VAR, ${}, ${1ABC}, ${A-BC}. These examples are captured with (1) but fail validation with (2) on which we can provide good error messages.

More info: https://stackoverflow.com/a/2821201/3626075