Add Checkstyle configuration for IntelliJ IDEA

.gitignore

@@ -8,7 +8,7 @@ target/
 .project
 .DS_Store
 .settings/
-.idea/
+.idea/*
 out/
 bin/
 intellij/
@@ -24,3 +24,6 @@ atlassian-ide-plugin.xml
 .checkstyle
 s101plugin.state
 .attach_pid*
+
+!.idea/checkstyle-idea.xml
+!.idea/externalDependencies.xml

.idea/checkstyle-idea.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="CheckStyle-IDEA">
+    <option name="configuration">
+      <map>
+        <entry key="active-configuration" value="PROJECT_RELATIVE:$PROJECT_DIR$/etc/checkstyle/checkstyle.xml:spring-security" />
+        <entry key="checkstyle-version" value="8.14" />
+        <entry key="copy-libs" value="false" />
+        <entry key="location-0" value="BUNDLED:(bundled):Sun Checks" />
+        <entry key="location-1" value="BUNDLED:(bundled):Google Checks" />
+        <entry key="location-2" value="PROJECT_RELATIVE:$PROJECT_DIR$/etc/checkstyle/checkstyle.xml:spring-security" />
+        <entry key="property-2.config_loc" value="$PROJECT_DIR$/etc/checkstyle" />
+        <entry key="scan-before-checkin" value="false" />
+        <entry key="scanscope" value="JavaOnlyWithTests" />
+        <entry key="suppress-errors" value="false" />
+      </map>
+    </option>
+  </component>
+</project>

.idea/externalDependencies.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ExternalDependencies">
+    <plugin id="CheckStyle-IDEA" />
+    <plugin id="org.jetbrains.plugins.gradle" />
+  </component>
+</project>