INTPYTHON-842 Prepare for langchain-mongodb 0.9.0 (#283)

INTPYTHON-842 

## Summary

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Prep for langchain-mongodb 0.9.0.

## Changes in this PR

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private) were added, removed, or edited to generate the desired outcome
explained in the above summary? -->
Update changelog and version.

## Test Plan
Standard tests
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### Screenshots (optional)
N/A
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## Checklist

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### Checklist for Author

- [x] Did you update the changelog (if necessary)?
- [x] Is the intention of the code captured in relevant tests?
- [x] If there are new TODOs, has a related JIRA ticket been created?
- [ ] Has a MongoDB Employee run [the patch build of this
PR](https://github.com/mongodb-labs/ai-ml-pipeline-testing?tab=readme-ov-file#running-a-patch-build-of-a-given-pr)?
N/A - docs only

### Checklist for Reviewer {@primary_reviewer}

- [ ] Does the title of the PR reference a JIRA Ticket?
- [ ] Do you fully understand the implementation? (Would you be
comfortable explaining how this code works to someone else?)
- [ ] Have you checked for spelling & grammar errors?
- [ ] Is all relevant documentation (README or docstring) updated?

## Focus Areas for Reviewer (optional)

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Author: blink1073

libs/langchain-mongodb/CHANGELOG.md

@@ -2,10 +2,17 @@
 
 ---
 
+## Changes in version 0.9.0 (2025/12/03)
+
+- Add visualization support to `MongoDBGraphStore` with optional `langchain_mongodb[viz]`.
+- Add `search_by_vector` method to `MongoDBAtlasVectorSearch`.
+- Add support for passing additional vector index options to the vector search index definition and related functions.
+
 ## Changes in version 0.8.0 (2025/11/18)
 
 - Update dependencies to align with LangChain 1.0, which is now the minimum supported version of LangChain.
   This includes adding `langchain_classic` as a dependency to support existing Retriever APIs.
+- Drop support for Python 3.9.
 
 ## Changes in version 0.7.2 (2025/10/30)
 

libs/langchain-mongodb/pyproject.toml

@@ -5,7 +5,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "langchain-mongodb"
-version = "0.8.0"
+version = "0.9.0"
 description = "An integration package connecting MongoDB and LangChain"
 readme = "README.md"
 requires-python = ">=3.10"