keep response headers on redirect (30x)

[nggit]

# case 1
response.set_header('Set-Cookie', 'xxx')
raise Forbidden  # 403, previous headers including cookies are cleared, OK so far

# case 2
response.set_header('Set-Cookie', 'xxx')
raise HTTPRedirect  # 30x, feel suck if also cleared. This PR prevents clear()

# case 3
# to reliably set headers on exception is via its kwargs
raise Forbidden('you are not allowed', set_cookie='xxx')  # **kwargs are translated as response headers

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
87.6% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud