Attachments of ArcGIS Rest Server Layer in QGIS

Question

Current Setup:

I have a connection to our ArcGIS Enterprise Portal (on-prem) using the Add ArcGIS Server Layer connection in QGIS. I have created an Desktop Application Item in the portal and I can connect using OAuth in QGIS to access the feature layers. The layer I am accessing in QGIS is an hosted feature layer (from Survey123) with attachments. I would like to show the attachments in the layer popup when clicking on a feature in QGIS.

Problem:

The problem is that in QGIS the attachments are not sent per default via the REST Api when requesting the data of a feature.

How I would like to solve this:

1. Access the token stored internally in QGIS after OAuth
2. Use an HTML Widget in the Attribute Form and make a REST call to the feature service to request all attachments / images.
3. Display the images within the HTML Widget

Currently I am stuck reading the token from the QgsApplication.authManager(). My code so far - unfortunately this only gives me the connection details but not the token:

authMgr = QgsApplication.authManager()
success, decrypted_config = authMgr.loadAuthenticationConfig(
    '791l69i',  # the id of the existing configuration to load (7 chars)
    QgsAuthMethodConfig(),  # a fresh new config object
    full=True,  # whether to decrypt the credentials
)

if success:
  print(decrypted_config.configMap())

Answer 1

I finally found a solution to my problem. I am using the openProject() macro in the Project Properties -> Macros section. It will query the self endpoint of the portal which describes the current authenticated user. Based on the OAuth2 it will authenticate myself. By doing so I will be able to read the Authorization header of the request which contains the token. This token is than saved as a project variable called project_esri_token and can be read within the HTML widget for further requests. Important to know is the my_authCfg property which is the ID of the authentication configuration which can be found in the top right corner of the OAuth2 authentication settings.

Macro:

from PyQt5.QtNetwork import QNetworkRequest, QNetworkReply
from PyQt5.QtCore import QUrl
from qgis.core import QgsApplication, QgsNetworkAccessManager, QgsProject

def openProject():
    auth_manager = QgsApplication.authManager()
    my_authCfg = '791l69i'
    network_manager = QgsNetworkAccessManager.instance()
    url = "https://<my-portal>/portal/sharing/rest/portals/self?f=json"
    request = QNetworkRequest(QUrl(url))
    reply = network_manager.blockingGet(request, my_authCfg)
    auth_header = request.rawHeader(b"Authorization").data().decode('utf-8')
    token = auth_header.replace("Bearer ", "")
    QgsProject.instance().setCustomVariables({"project_esri_token": token})    
    pass