Add External Data extension, with config for SnipeIT

Dockerfile

@@ -67,3 +67,8 @@ RUN git clone --depth 1 -b $MEDIAWIKI_BRANCH \
 RUN git clone --depth 1 -b $MEDIAWIKI_BRANCH \
     https://gerrit.wikimedia.org/r/mediawiki/extensions/TemplateData \
     /var/www/html/extensions/TemplateData
+
+# https://www.mediawiki.org/wiki/Extension:External_Data
+RUN git clone --depth 1 \
+    https://gerrit.wikimedia.org/r/mediawiki/extensions/ExternalData \
+    /var/www/html/extensions/ExternalData

LocalSettings.php

@@ -227,3 +227,17 @@ $wgVirtualRestConfig['modules']['parsoid'] = array(
 wfLoadExtension( 'TemplateData' );
 
 require_once "$IP/extensions/Widgets/Widgets.php";
+
+wfLoadExtension( 'ExternalData' );
+$edgStringReplacements['SNIPEIT_URL'] = 'https://inventory.claremontmakerspace.org';
+$edgAllowExternalDataFrom = 'SNIPEIT_URL';
+// TODO: Use ExternalDataBeforeWebCall to set the headers only for
+//       snipeit API calls. Only matters if other domains are added to
+//       the whitelist.
+$edgHTTPOptions = [
+    'headers' => [
+        'Accept' => 'application/json',
+        'Content-Type' => 'application/json',
+        'Authorization' => 'Bearer '.$secrets['SnipeITAPIKey']
+    ]
+];