Added Release notes for voyager 1.8.9 release (#2185)

RELEASE_NOTES.md

@@ -4,6 +4,33 @@
 
 Included here are the release notes for the [YugabyteDB Voyager](https://docs.yugabyte.com/preview/migrate/) v1 release series. Content will be added as new notable features and changes are available in the patch releases of the YugabyteDB v1 series.
 
+## v1.8.9 - January 14, 2025
+
+### New Features
+- Implemented a new algorithm for migration complexity determination that accounts for all potential issues, including unsupported query constructs, PL/pgSQL objects, and incompatible data types.
+- Introduced migration complexity explanations in the PostgreSQL assessment report, summarising high-impact issues and illustrating how the overall complexity level is determined.
+
+### Enhancements
+- Enhanced Assessment and Schema Analysis reports to detect unsupported PostgreSQL features from PG 12 up to PG 17, including:
+  - Regexp functions (`regexp_count`, `regexp_instr`, `regexp_like`)
+  - Security Invoker Views
+  - JSON **constructor** and JSON **Query functions**
+  - IS_JSON predicate clauses(`IS_JSON`, `IS JSON SCALAR`, `IS JSON OBJECT`, `IS JSON ARRAY`)
+  - Aggregate functions like `anyvalue`, `range_agg`, `range_intersect_agg`
+  - COPY command syntax such as `COPY FROM ... WHERE` and `COPY ... ON_ERROR`
+  - **Multirange datatypes** like `int4multirange`, `int8multirange`, `datemultirange` etc..
+  - `FETCH FIRST … WITH TIES` subclause in `SELECT` statement
+  - Foreign Key referencing a partitioned table
+  - JSONB Subscripting in DML, DDL or PL/PGSQL
+  - `UNIQUE NULLS NOT DISTINCT` in `CREATE/ALTER TABLE` statement
+  - The **deterministic** attribute in `CREATE COLLATION`
+  - `MERGE` statements 
+
+### Bug Fixes
+- Fixed an [issue](https://github.com/yugabyte/yb-voyager/issues/2034) where import data failed for tables whose datafile paths exceeded 250 characters. The fix is backward compatible, allowing migrations started with older voyager version to continue seamlessly.
+- Fixed an issue where logic for detecting unsupported PostgreSQL versions was giving false positives.
+
+
 ## v1.8.8 - December 24, 2024
 
 ### Enhancements