Remove embedding from Document

[markpollack]

This was a design decision way back taken from how langchain (python) was designed. In practice, this doesn't seem useful. It acts like a sort of cache, if you are writing the same document to the vector store multiple times, which doesn't seem realistic. If you have a use case for keeping the embedding in the Document, please comment.

[ThomasVitale]

The SimpleVectorStore relies on the presence of the "embedding" field in Document.

[iAMSagar44]

The AzureVectorStore also relies on the presence of the "embedding" field in Document. The doAdd method has the following line of code in the 1.0.0-M4 version of Spring AI.
searchDocument.put(EMBEDDING_FIELD_NAME, document.getEmbedding());

[ilayaperumalg]

The SimpleVectorStore relies on the presence of the "embedding" field in Document.

This PR #1822 addresses this.

[markpollack]

We need to review all the vector store impls and make appropriate modifications. I noticed the Neo4jVectorStore also uses the 'getEmbeddings' method as sort of simple data structure to pass things along while adding. It can be refactored.

[ThomasVitale]

If possible, it would be great to get #1794 merged before start removing the "embedding" field, mostly to avoid many many merge conflicts since they touch the same code area 😅

[ilayaperumalg]

We need to review all the vector store impls and make appropriate modifications. I noticed the Neo4jVectorStore also uses the 'getEmbeddings' method as sort of simple data structure to pass things along while adding. It can be refactored.

Created #1826 to track this.