Authenticate using User JWT-Token

[aMahanna]

Closes #238

Introduces a user_token parameter to the arango.client.ArangoClient.db method to build a JwtConnection object without a username/password and without auth_method="jwt"

also introduces set_token to arango.connection.JwtConnection and arango.connection.JwtSuperuserConnection

import os
from arango import ArangoClient

token = os.environ["ARANGODB_USER_JWT"]
db = ArangoClient().db(user_token=token)
db = ArangoClient().db(username=..., password=..., user_token=token) # Valid, but ignores `username` and `password` params

db.conn.set_token(token=...) # Valid
db.conn.refresh_token() # Raises `arango.exceptions.JWTRefreshError`, since `username/password` is not set
ArangoClient().db(user_token=expired_token) # Raises `JWTExpiredError`

[codecov-commenter]

Codecov Report

Merging #293 (74e1b0b) into main (744a6e9) will decrease coverage by 0.57%.
Report is 22 commits behind head on main.
The diff coverage is 92.05%.

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@@            Coverage Diff             @@
##             main     #293      +/-   ##
==========================================
- Coverage   99.01%   98.44%   -0.57%     
==========================================
  Files          26       26              
  Lines        3958     4062     +104     
==========================================
+ Hits         3919     3999      +80     
- Misses         39       63      +24     

Files	Coverage Δ
arango/aql.py	95.04% <100.00%> (ø)
arango/client.py	98.46% <100.00%> (+0.04%)	⬆️
arango/cluster.py	100.00% <100.00%> (ø)
arango/exceptions.py	100.00% <100.00%> (ø)
arango/executor.py	99.35% <100.00%> (-0.13%)	⬇️
arango/http.py	100.00% <ø> (ø)
arango/job.py	100.00% <100.00%> (ø)
arango/request.py	94.44% <100.00%> (ø)
arango/typings.py	100.00% <100.00%> (ø)
arango/utils.py	87.50% <100.00%> (-12.50%)	⬇️
... and 3 more

[geenen124]

LGTM!