Replace {project-name} attribute in document title for downstream

The downstream tool does not handle attributes in project title so we
need to replace the attribute ourselves.

The attribute is only replaced in the document title, the rest of the
document uses standard attributes.

I pushed an example in datasource.adoc.

(cherry picked from commit 22e6403)

docs/src/main/asciidoc/datasource.adoc

@@ -4,7 +4,7 @@ and pull requests should be submitted there:
 https://github.com/quarkusio/quarkus/tree/main/docs/src/main/asciidoc
 ////
 [id="datasources"]
-= Configure data sources in Quarkus
+= Configure data sources in {project-name}
 include::_attributes.adoc[]
 :diataxis-type: reference
 :categories: data,getting-started,reactive

docs/src/main/java/io/quarkus/docs/generation/AssembleDownstreamDocumentation.java

@@ -50,6 +50,9 @@ public class AssembleDownstreamDocumentation {
     private static final String SOURCE_BLOCK_PREFIX = "[source";
     private static final String SOURCE_BLOCK_DELIMITER = "--";
 
+    private static final String PROJECT_NAME_ATTRIBUTE = "{project-name}";
+    private static final String RED_HAT_BUILD_OF_QUARKUS = "Red Hat build of Quarkus";
+
     private static final String QUARKUS_IO_GUIDES_ATTRIBUTE = "{quarkusio-guides}";
 
     private static final Map<Pattern, String> TABS_REPLACEMENTS = Map.of(
@@ -301,10 +304,17 @@ private static void copyAsciidoc(Path sourceFile, Path targetFile, Set<String> d
         boolean findDelimiter = false;
         String currentSourceBlockDelimiter = "----";
         int lineNumber = 0;
+        boolean documentTitleFound = false;
 
         for (String line : guideLines) {
             lineNumber++;
 
+            if (!documentTitleFound && line.startsWith("= ")) {
+                // this is the document title
+                rewrittenGuide.append(line.replace(PROJECT_NAME_ATTRIBUTE, RED_HAT_BUILD_OF_QUARKUS) + "\n");
+                documentTitleFound = true;
+                continue;
+            }
             if (inSourceBlock) {
                 if (findDelimiter) {
                     rewrittenGuide.append(line + "\n");