Add functions to generate DDL for recreating roles.

pg_get_role_ddl(regrole) returns the DDL needed to recreate a role
as a single text string.  pg_get_role_ddl_statements(regrole) returns
the same thing as a set of rows, one per DDL statement.

The output includes the CREATE ROLE statement with all role attributes,
plus any ALTER ROLE SET configuration parameters (both role-wide and
database-specific settings).

Passwords cannot be included, since we can only see the hashed values.
System roles (names starting with "pg_") are rejected, since users
shouldn't be recreating those anyway.

Co-authored-by: Mario Gonzalez <gonzalemario@gmail.com>
Co-authored-by: Bryan Green <dbryan.green@gmail.com>
Reviewed-by: li carol <carol.li2025@outlook.com>

Author: 2 people

doc/src/sgml/func/func-info.sgml

@@ -2174,7 +2174,61 @@ SELECT currval(pg_get_serial_sequence('sometable', 'id'));
      </tbody>
     </tgroup>
    </table>
-
+  <table id="functions-object-ddl-table">
+    <title>Object DDL Functions</title>
+    <tgroup cols="1">
+     <thead>
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">Function</para>
+        <para>Description</para>
+       </entry>
+      </row>
+     </thead>
+     <tbody>
+      <row>
+       <entry role="func_table_entry">
+        <para role="func_signature">
+         <indexterm>
+          <primary>pg_get_role_ddl</primary>
+         </indexterm>
+         <function>pg_get_role_ddl</function> ( <parameter>role</parameter> <type>regrole</type> )
+         <returnvalue>text</returnvalue>
+        </para>
+        <para>
+         Returns the DDL commands that would recreate the given role as a single text string.
+         The result includes the <command>CREATE ROLE</command> statement and any
+         <command>ALTER ROLE</command> statements needed to set role configuration parameters.
+         Password information is never included in the output.
+        </para>
+        <para>
+         Returns <literal>NULL</literal> if the role does not exist.
+        </para>
+       </entry>
+      </row>
+      <row>
+       <entry role="func_table_entry">
+        <para role="func_signature">
+         <indexterm>
+          <primary>pg_get_role_ddl_statements</primary>
+         </indexterm>
+         <function>pg_get_role_ddl_statements</function> ( <parameter>role</parameter> <type>regrole</type> )
+         <returnvalue>setof text</returnvalue>
+        </para>
+        <para>
+         Returns the DDL commands that would recreate the given role as a set of rows,
+         with each statement returned as a separate row. The first row contains the
+         <command>CREATE ROLE</command> statement, followed by any <command>ALTER ROLE</command>
+         statements needed to set role configuration parameters. This format is useful for
+         programmatic processing or when you want to filter or analyze individual statements.
+        </para>
+        <para>
+         Returns an empty set if the role does not exist.
+        </para>
+       </entry>
+      </row>
+     </tbody>
+    </tgroup>
+  </table>
   <para>
    Most of the functions that reconstruct (decompile) database objects
    have an optional <parameter>pretty</parameter> flag, which