Fix db_ddl.sql: align with authoritative openas2-schema.xml

[ricardopsj]

Summary

Aligns Server/src/config/db_ddl.sql with the authoritative schema in Server/src/resources/db/openas2-schema.xml. The two had drifted: most notably, db_ddl.sql was missing the SENT_FILE_NAME column that DbTrackingModule writes on every outbound, plus several other smaller divergences (column types, defaults).

Fixes the bug described in #537 (created alongside this PR).

What's in the change

• SENT_FILE_NAME VARCHAR(255) added immediately after FILE_NAME (same position as in the XML).
• MSG_ID, PRIOR_MSG_ID, MDN_ID, MDN_RESPONSE, STATE_MSG promoted from unbounded VARCHAR to LONGVARCHAR, matching the XML.
• Column defaults added so the SQL matches the XML's behavior on fresh installs:
  • IS_RESEND DEFAULT 'N'
  • RESEND_COUNT DEFAULT 0
  • CREATE_DT DEFAULT CURRENT_TIMESTAMP
• Header comment added pointing maintainers at openas2-schema.xml as the single source of truth, so the two files don't drift again.
• Server/src/test/resources/config/db_ddl.sql mirrored with the same content to keep the test fixture aligned.

Why this matters

create_db_table.sh (the "official" bootstrap path) needs Apache Ant on the host and TCP 9092 open on the H2 server. Hardened deployments routinely:

• skip ant (not on the runtime image), and
• set tcp_server_start="false" in DbTrackingModule so H2 stays in embedded/file mode (no exposed 9092).

In those deployments the only viable bootstrap is to apply db_ddl.sql directly via org.h2.tools.RunScript against the embedded .mv.db file. That's the path this PR fixes.

Backwards compatibility

• Pure additive on the schema (one new column, defaults on existing columns, type widenings). No data migration needed for fresh installs.
• For existing installs that already created the table from the old db_ddl.sql and want to upgrade in place:

  ALTER TABLE msg_metadata ADD COLUMN sent_file_name VARCHAR(255);

  (DbTrackingModule inserts will work after this even without restarting.)

How this was tested

• Bootstrapped a fresh H2 file with the new db_ddl.sql using org.h2.tools.RunScript on Debian 13 + OpenJDK 21.
• Sent an outbound message; DbTrackingModule wrote a complete row including sent_file_name.
• Smoke test repeated on a second independent deployment (same OS/JDK stack), same result.

Notes for reviewers

• The XML schema (openas2-schema.xml) remains the source of truth; this PR just brings the convenience SQL up to date with it.
• A follow-up could consider auto-generating db_ddl.sql from the XML at build time so they cannot drift again. Out of scope for this PR — happy to do it as a second PR if maintainers prefer.

[uhurusurfa]

Thanks for the fixes.
The next release for OpenAS2 will be a major release using Hibernate to manage the schema so the use of DDL utils and the XML schema will soon be dropped.