Implement payment backends and interaction

Advances #3 (closed)

aleksis/apps/tezor/apps.py

+from django.apps import apps
+
 from aleksis.core.util.apps import AppConfig
+from aleksis.core.util.core_helpers import get_site_preferences
 
 
 class DefaultConfig(AppConfig):
@@ -11,3 +14,39 @@ class DefaultConfig(AppConfig):
     }
     licence = "EUPL-1.2+"
     copyright_info = (([2022], "Dominik George", "dominik.george@teckids.org"),)
+
+    def ready(self):
+        from django.conf import settings  # noqa
+        settings.PAYMENT_MODEL = "tezor.Invoice"
+        settings.PAYMENT_VARIANTS = {
+            "dummy": ("payments.dummy.DummyProvider", {})
+        }
+
+        for app_config in apps.app_configs.values():
+            if hasattr(app_config, "get_payment_variants"):
+                variants = app_config.get_payment_variants()
+                for name, config in variants.items():
+                    if name not in settings.PAYMENT_VARIANTS:
+                        settings.PAYMENT_VARIANTS[name] = config
+
+    def get_payment_variants(self):
+        prefs = get_site_preferences()
+        variants = {}
+
+        if prefs["payments__sofort_api_id"]:
+            variants["sofort"] = ("payments.sofort.SofortProvider", {
+                "id": prefs["payments__sofort_api_id"],
+                "key": prefs["payments__sofort_api_key"],
+                "project_id": prefs["payments__sofort_project_id"],
+                "endpoint": "https://api.sofort.com/api/xml",
+            })
+
+        if prefs["payments__paypal_client_id"]:
+            variants["paypal"] = ("payments.paypal.PaypalProvider", {
+                "client_id": prefs["payments__paypal_client_id"],
+                "secret": prefs["payments__paypal_secret"],
+                "capture": not prefs["payments__paypal_capture"],
+                "endpoint": "https://api.paypal.com",
+            })
+
+        return variants