[OpenSearch] Add chunks specific to an app_id if present

[deshraj]

Description

Noticed that currently Embedchain indexes all the document chunks to the same OpenSearch index which then causes issues if you are trying to use different app instances using opensearch. This leads to document getting deleted from the Opensearch index despite not wanting to touch that document since it was a part of a different embedchain app instantiation.

This PR fixes this issue. Updated the test to make sure it works fine.

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• Unit Test

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

[codecov]

Codecov Report

Attention: 23 lines in your changes are missing coverage. Please review.

Files	Coverage Δ
embedchain/chunkers/base_chunker.py	100.00% <100.00%> (ø)
embedchain/chunkers/images.py	100.00% <100.00%> (ø)
embedchain/embedchain.py	72.76% <50.00%> (-1.13%)	⬇️
embedchain/vectordb/opensearch.py	0.00% <0.00%> (ø)

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