import: check that matched key is not a substring of the replacement key

[WeidiDeng]

Fix issue reported on community.

When importing arguments, regex will usually match a substring of the key, this change detects if it's a substring match.

Personally I think caddy shouldn't allow braces in the replacer as it has other implications. But this will do for now.

[francislavoie]

Thanks! Glad you could find this ☺️

[mholt]

Thanks Weidi.

Personally I think caddy shouldn't allow braces in the replacer as it has other implications.

You mean { } braces?

[WeidiDeng]

I mean disallow keys like test{test, the underlying problem is replacer feed the charactes between the opening brace and the first closing brace, and there can be opening braces in between.

Normally this isn't a problem, but in JSON, it is. And if replacer is configured to return an error upon an unknown key, it will.