check_error.go uses html/template, corrupting JSON API error messages

[cinar]

Problem

check_error.go imports html/template and uses it to render localized error messages:

import "html/template"
...
tmpl, err := template.New("error").Parse(getLocalizedErrorMessage(locale, c.Code))

html/template contextually auto-escapes its output for safe embedding in HTML. For a library whose primary consumer is a JSON API error body (CheckErrors.JSON()), this means any error data containing <, >, &, or " — for example a regex pattern or a user-supplied value echoed into an error message via template data — gets corrupted into <, >, &, " in the JSON payload.

Fix

Switch the import to text/template, which performs no such escaping and is the correct choice for plain-text/JSON message rendering.