Exchange token for proxy

[chaen]

• Implement an DB class to get a proxy from the ProxyDB
• Add a route to return the Proxy GET /auth/proxy
• Implement the Proxy delegation mechanism locally to have a proxy lasting as long as the refresh token with the same group. Check that the properties in the token matches those defined in the CS for the said group. (@chaen to provide a standalone script to perform delegation)
• Add the VOMS extension (voms-proxy-fake is fine for now)
• Call the route from the cli

The proxy delegation mechanism is documented here https://github.com/DIRACGrid/DIRAC/blob/4b5a8216da61ef5cb07e53f2e3a5ad2b4f01aad6/src/DIRAC/Core/Security/test/Test_X509Chain.py#L508-L570

[chaen]

Create a delegated proxy from one as input:

import sys

from DIRAC.Core.Utilities.ReturnValues import returnValueOrRaise
from DIRAC.Core.Security.m2crypto.X509Chain import X509Chain

input_proxy_file = sys.argv[1]
delegated_proxy_file = sys.argv[2]
lifetime = int(sys.argv[3])

# Load the initial proxy
proxyChain = X509Chain()
returnValueOrRaise(proxyChain.loadProxyFromFile(input_proxy_file))

# And "delegate"
returnValueOrRaise(proxyChain.generateProxyToFile(delegated_proxy_file, diracGroup="lhcb_user",lifetime=lifetime))

and then we add the voms extensions with something like that:

https://github.com/DIRACGrid/DIRAC/blob/271a3e110edc925b2c7f0be75b57238c520fdc8d/src/DIRAC/Core/Security/VOMS.py#L269-L285

(that means the VOMS servers need to be configured anyway on the diracx servers 🤮