Use uppercase version of configured HTTP headers

Before Authconfig was introduced the helper method to get the
HTTP headers from config also changed them into uppercase.
Use uppercase version of the the auth headers from AuthConfig.

Change-Id: Iec0884d2c9d8880c19a010fcef926b70aba66ba0
diff --git a/src/main/java/com/googlesource/gerrit/plugins/saml/SamlWebFilter.java b/src/main/java/com/googlesource/gerrit/plugins/saml/SamlWebFilter.java
index 684f93a..7e51f36 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/saml/SamlWebFilter.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/saml/SamlWebFilter.java
@@ -111,10 +111,10 @@
     saml2Client = new SAML2Client(samlClientConfig);
     authHeaders =
         Sets.newHashSet(
-            auth.getLoginHttpHeader(),
-            auth.getHttpDisplaynameHeader(),
-            auth.getHttpEmailHeader(),
-            auth.getHttpExternalIdHeader());
+            auth.getLoginHttpHeader().toUpperCase(),
+            auth.getHttpDisplaynameHeader().toUpperCase(),
+            auth.getHttpEmailHeader().toUpperCase(),
+            auth.getHttpExternalIdHeader().toUpperCase());
     if (authHeaders.contains("") || authHeaders.contains(null)) {
       throw new RuntimeException("All authentication headers must be set.");
     }
@@ -320,13 +320,13 @@
     @Override
     public String getHeader(String name) {
       String nameUpperCase = name.toUpperCase();
-      if (auth.getLoginHttpHeader().equals(nameUpperCase)) {
+      if (auth.getLoginHttpHeader().toUpperCase().equals(nameUpperCase)) {
         return user.getUsername();
-      } else if (auth.getHttpDisplaynameHeader().equals(nameUpperCase)) {
+      } else if (auth.getHttpDisplaynameHeader().toUpperCase().equals(nameUpperCase)) {
         return user.getDisplayName();
-      } else if (auth.getHttpEmailHeader().equals(nameUpperCase)) {
+      } else if (auth.getHttpEmailHeader().toUpperCase().equals(nameUpperCase)) {
         return user.getEmail();
-      } else if (auth.getHttpExternalIdHeader().equals(nameUpperCase)) {
+      } else if (auth.getHttpExternalIdHeader().toUpperCase().equals(nameUpperCase)) {
         return user.getExternalId();
       } else {
         return super.getHeader(name);