ASF: add fixeddecimal license and RAT exclusions

Add compliance metadata for the newly imported contrib/fixeddecimal extension.

- Add fixeddecimal license notice entry under the
  "Apache Cloudberry includes codes from" section in LICENSE
  (PostgreSQL License, with a pointer to licenses/LICENSE-fixeddecimal.txt).
- Add licenses/LICENSE-fixeddecimal.txt with fixeddecimal attribution and
  PostgreSQL license text.
- Add Apache RAT exclusion for contrib/fixeddecimal/** in pom.xml, and place
  it in the Cloudberry-origin section (not the Greenplum section).

This keeps license attribution and RAT classification aligned with
fixeddecimal’s origin and repository organization.

Author: tuhaihe

LICENSE

@@ -338,6 +338,12 @@ Apache Cloudberry includes codes from
 
       see licenses/LICENSE-citusdata.txt
 
+----------------------------
+   PostgreSQL License
+
+      contrib/fixeddecimal/*
+      see licenses/LICENSE-fixeddecimal.txt
+
 ----------------------------
    Apache License - Version 2.0
 

licenses/LICENSE-fixeddecimal.txt

@@ -0,0 +1,32 @@
+Copyright (c) 2015, PostgreSQL Global Development Group
+
+fixeddecimal is licensed under the PostgreSQL license, the same license
+as PostgreSQL. It was originally developed by 2ndQuadrant and later
+novated to the PostgreSQL Global Development Group.
+
+A copy of the PostgreSQL license is below:
+
+--------------
+PostgreSQL Database Management System
+(formerly known as Postgres, then as Postgres95)
+
+Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
+
+Portions Copyright (c) 1994, The Regents of the University of California
+
+Permission to use, copy, modify, and distribute this software and its
+documentation for any purpose, without fee, and without a written agreement
+is hereby granted, provided that the above copyright notice and this
+paragraph and the following two paragraphs appear in all copies.
+
+IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR
+DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
+LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
+DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
+
+THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
+INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATIONS TO
+PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.

pom.xml

@@ -1272,6 +1272,11 @@ code or new licensing patterns.
             <exclude>src/include/task/task_states.h</exclude>
             <exclude>src/include/task/job_metadata.h</exclude>
 
+            <!-- The following files are from fixeddecimal under PostgreSQL
+                 license, introduced by Cloudberry.
+            -->
+            <exclude>contrib/fixeddecimal/**</exclude>
+
             <!-- The following files are used by PAX as the 
                  submodules or created originally by Cloudberry.
             -->