feat(infra): Keycloak with four mock realms (closes #3) (#43)

infra/keycloak/realms/digid-realm.json

@@ -0,0 +1,43 @@
+{
+  "realm": "digid",
+  "enabled": true,
+  "displayName": "Mock DigiD",
+  "clients": [
+    {
+      "clientId": "big-portal",
+      "enabled": true,
+      "publicClient": true,
+      "standardFlowEnabled": true,
+      "directAccessGrantsEnabled": true,
+      "redirectUris": ["*"],
+      "webOrigins": ["*"],
+      "protocolMappers": [
+        {
+          "name": "bsn",
+          "protocol": "openid-connect",
+          "protocolMapper": "oidc-usermodel-attribute-mapper",
+          "config": {
+            "user.attribute": "bsn",
+            "claim.name": "bsn",
+            "jsonType.label": "String",
+            "id.token.claim": "true",
+            "access.token.claim": "true",
+            "userinfo.token.claim": "true"
+          }
+        }
+      ]
+    }
+  ],
+  "users": [
+    {
+      "username": "jan-burger",
+      "enabled": true,
+      "firstName": "Jan",
+      "lastName": "Burger",
+      "email": "jan.burger@example.nl",
+      "emailVerified": true,
+      "credentials": [{ "type": "password", "value": "test123", "temporary": false }],
+      "attributes": { "bsn": ["123456782"] }
+    }
+  ]
+}