Switch the Mediawiki config to the new LDAP dir structure

* Use a new read-only account instead of the admin LDAP account
* Disable the LDAPAuthorization plugin. The LDAPAuthentication2 plugin
is still used to authenticate users, but every kosmos.org user has
access to the wiki. See
https://www.mediawiki.org/wiki/Extension:PluggableAuth for the
distinction between authentication and authorization

Refs #127

data_bags/credentials/mediawiki.json

@@ -1,15 +1,31 @@
 {
   "id": "mediawiki",
   "antispam_key": {
-    "encrypted_data": "0geoVeZ/umKaBCbhDfxkacWt4sWQBHrRxYGTSsaC5gw=\n",
-    "iv": "YxwNvI3HXeMZRHFpv+QLcQ==\n",
-    "version": 1,
-    "cipher": "aes-256-cbc"
+    "encrypted_data": "OD5RrVaQoUFbGV1Xs6i3hqZ024IJsbOC4CAWzrw5jQ==\n",
+    "iv": "8sfvTg7uGe1ofS2C\n",
+    "auth_tag": "hquilck+xxOQqHjE+szPgA==\n",
+    "version": 3,
+    "cipher": "aes-256-gcm"
   },
   "db_pass": {
-    "encrypted_data": "aQ1soJeRPq9TQuDglkXrl10rIx5RpBNd5HltKVsYgLHedS5zXy8ylBhNdgBW\nb6slPhsbAB9d45aZAac7LUSbMIDIg8P+Zdx/0+IaEuwcpuQ=\n",
-    "iv": "RDS39dqjBPO0CyyANsa+2g==\n",
-    "version": 1,
-    "cipher": "aes-256-cbc"
+    "encrypted_data": "2IntmJdBmfGyHghAXDJnaew58u9dvjKCz/q1Uivs8Q+nH3wVqARkf52BIHhZ\nbIHY3cy50EwcKTxDcr1arQFmb88cKBxt\n",
+    "iv": "pkCrp07s4LJfaPmq\n",
+    "auth_tag": "yBsriBc/X2bP6v25NY3cSg==\n",
+    "version": 3,
+    "cipher": "aes-256-gcm"
+  },
+  "ldap_user": {
+    "encrypted_data": "l/Q63Mvm/tANfvZ+1ijjTB1lpirOhAjWDz4k+R1OkzYIXQNwo6VM2saTH2eu\nBNHFLTyUSMqzlAcq6OvH++En05wk\n",
+    "iv": "y+n/Lo8t6O3Ab4/+\n",
+    "auth_tag": "7eHYjF8A0T611Y+JT1GeJg==\n",
+    "version": 3,
+    "cipher": "aes-256-gcm"
+  },
+  "ldap_password": {
+    "encrypted_data": "+qYb9F/f9QRRCTsMoRIyWWVQyCSLcQRHSPWD2Nf7z7Kauywh1zIg\n",
+    "iv": "sivNzq6G+mScbRnn\n",
+    "auth_tag": "ybUpDlIOJm0bsqlY5qt1xA==\n",
+    "version": 3,
+    "cipher": "aes-256-gcm"
   }
 }