Use Device Authorization flow

[DavidS-ovm]

This replaces a bunch of cumbersome code with OAuth2 built-in functionality also ensuring that the actual device is authorized with no MitM attack.

This reverts the auth0 config flag removal to be able to test against non-prod environments.

Fixes #174

Example session:

vscode ➜ /workspace/cli (main) $ rm /home/vscode/.overmind/token.json
vscode ➜ /workspace/cli (main) $ go run main.go request --query-type ec2-instance --query-method list --log debug
DEBU Error reading local token, ignoring: stat /home/vscode/.overmind/token.json: no such file or directory 
Go to https://om-dogfood.eu.auth0.com/activate?user_code=MJRB-ZNPH and verify this code: MJRB-ZNPH
INFO Authenticated successfully ✅                 
DEBU Saved token to /home/vscode/.overmind/token.json 
INFO received items                                error="<nil>"
INFO Query:
{
  "type": "ec2-instance",
  "method": 1,
  "recursionBehaviour": {},
  "scope": "*",
  "UUID": "1W9uBVpRR+O4JWLwnx4Pbw==",
  "deadline": {
    "seconds": 1708033535,
    "nanos": 454381490
  }
}  uuid=d56f6e05-5a51-47e3-b825-62f09f1e0f6f
DEBU query status update                           query=d56f6e05-5a51-47e3-b825-62f09f1e0f6f status=STARTED
INFO new item                                      item=944651592624.eu-west-2.ec2-instance.i-0967d3ae34899b1e8
INFO new item                                      item=944651592624.eu-west-2.ec2-instance.i-08b0f2a06b23905d5
INFO new item                                      item=944651592624.eu-west-2.ec2-instance.i-0da03dca5c6d870d9
DEBU query status update                           query=d56f6e05-5a51-47e3-b825-62f09f1e0f6f status=FINISHED
INFO all queries done                              edgesReceived=0 itemsReceived=3 queriesStarted=1
vscode ➜ /workspace/cli (main) $ go run main.go request --query-type ec2-instance --query-method list --log debug
DEBU Using local token from /home/vscode/.overmind/token.json 
INFO received items                                error="<nil>"
INFO Query:
{
  "type": "ec2-instance",
  "method": 1,
  "recursionBehaviour": {},
  "scope": "*",
  "UUID": "b0UwRriQRFuYieTNaKmocg==",
  "deadline": {
    "seconds": 1708033540,
    "nanos": 671043720
  }
}  uuid=6f453046-b890-445b-9889-e4cd68a9a872
DEBU query status update                           query=6f453046-b890-445b-9889-e4cd68a9a872 status=STARTED
INFO new item                                      item=944651592624.eu-west-2.ec2-instance.i-0967d3ae34899b1e8
INFO new item                                      item=944651592624.eu-west-2.ec2-instance.i-0da03dca5c6d870d9
INFO new item                                      item=944651592624.eu-west-2.ec2-instance.i-08b0f2a06b23905d5
DEBU query status update                           query=6f453046-b890-445b-9889-e4cd68a9a872 status=FINISHED
INFO all queries done                              edgesReceived=0 itemsReceived=3 queriesStarted=1
vscode ➜ /workspace/cli (main) $