fix: Sanitize sensitive headers and request bodies in JIRAError.__str__ to prevent credential leakage

[niljub]

This PR addresses a security issue in JIRAError.__str__ where full request and response details are included in the exception string, including sensitive headers and potentially sensitive request bodies.

When a JIRAError is logged, this can unintentionally leak:

• Authorization headers (API tokens, OAuth tokens, Basic Auth credentials)
• Cookie / Set-Cookie headers (session identifiers)
• Request bodies containing secrets (e.g. passwords during user creation or update)

This PR introduces sanitization logic to mask sensitive headers and redact potentially sensitive request body content before rendering the exception string.