feat: Add AWS bedrock embeddings to embedding encoder

[jlonge4]

Proposed Changes:

Add AWS Bedrock embedding retriever to support embedding queries/documents with titan embeddings model.

How did you test it?

manual verification

Notes for the reviewer

haystack/nodes/retriever/embedding_encoder
haystack/nodes/retriever/dense

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.
• I documented my code
• I ran pre-commit hooks and fixed any issue

[coveralls]

Pull Request Test Coverage Report for Build 6977754646

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 146 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.02%) to 40.094%

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Files with Coverage Reduction	New Missed Lines	%
nodes/retriever/dense.py	54	28.01%
nodes/retriever/_embedding_encoder.py	92	35.41%

Totals
Change from base Build 6973422803:	-0.02%
Covered Lines:	10699
Relevant Lines:	26685

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💛 - Coveralls

[anakin87]

Hey @jlonge4, we are very busy with the upcoming 2.0 release these days.

So probably the review process may be a bit long... Please bear with us.

[jlonge4]

@anakin87 No worries! I totally understand

[jlonge4]

@tstadel no worries I appreciate the feedback! Everything should be implemented, however some weird failures related to files I hadn't even touched that I didn't get last time.

[jlonge4]

@anakin87 was that a merge in the wrong direction? 😅

[anakin87]

I fixed mypy and pylint errors.

In general, it looks good, but I haven't tried these changes locally....

@tstadel can you take another look?

[tstadel]

@anakin87 @jlonge4 I did some final refactorings and fixed two things:

• rename session_token to aws_session_token to be consistent with boto3
• set truncate: 'RIGHT' for cohere request payloads according to https://docs.aws.amazon.com/bedrock/latest/userguide/model-parameters-embed.html (with END it did not work)

Also for cohere we use batch mode now. I made some final tests locally to ensure doc and query embeddings are working with titan and cohere models.

So from my side we can merge now :-)

[tstadel]

@anakin87 wait I've found another thing to improve:

• we should throw AWSConfigurationError instead of ValueError if an error occurs during boto3 session init. I'll quickly fix that.

[tstadel]

@anakin87 ok now we're good to go.

[anakin87]

@jlonge4 @tstadel
Thanks for your efforts!

[jlonge4]

@tstadel @anakin87 thank you both so much for the help and patience!