jwt-parser - show full date with timezone for date claims

[Lukkasss]

Proposed change

Render the date-based JWT claims (iat, exp, nbf) using the full date representation instead of a bare locale date + time.

Before

iat (Issued At) 1516239022 (17/01/2018 23:30:22)

After

iat (Issued At) 1516239022 (Wed Jan 17 2018 23:30:22 GMT-0200 (Horário de Verão de Brasília))

Why

When investigating or debugging a JWT, the timestamp is often very important and displaying the full date right away helps a lot. The previous output (17/01/2018 23:30:22) hid two things that matter for that analysis:

• The UTC offset (GMT-0200), so you can immediately see how the token's time relates to UTC without doing the math in your head.
• The timezone name, which makes it unambiguous which local time you're looking at.

Seeing the complete date picture lets you reason about a token's validity straight away instead of guessing what locale the short date was rendered in.

How

dateFormatter now returns date.toString() instead of ${date.toLocaleDateString()} ${date.toLocaleTimeString()}.

each user sees the timestamp in their own browser's timezone and language.

Notes about the change

• Single-line change in src/tools/jwt-parser/jwt-parser.service.ts.
• No new dependencies.
• Applies to all three date claims (iat, exp, nbf) since they share the same formatter.