Regex patterns containing backticks generate invalid Go

[piotrekwitkowski]

Regex patterns are emitted as raw Go string literals. A pattern containing a backtick therefore produces invalid generated Go source.

For example, this schema pattern includes the permitted HTTP token characters:

pattern: "^[!#$%&'*+.^_`|~0-9A-Za-z-]+$"

The generated raw string is terminated by the embedded backtick, and the generated package does not compile.

#378 and #380 address related quoting problems but do not cover embedded backticks.

Expected behavior:

• Generated Go compiles when a regex pattern contains a backtick.
• The regex received at runtime is identical to the pattern in the schema.
• Patterns containing backslashes, quotes, Unicode, or control characters are represented without changing their value.