[Feature] Add support for metadata filtering on search API

[deshraj]

Description

Requested by one of our users on the slack group.

This PR adds support for following:

• Metadata filtering on the search API
• Add support for two ways to do metadata filtering: 1) Passing simple key value filters, 2) Passing raw query for the vector database
• Update docs for the same
• Refactor code

Type of change

• New feature (non-breaking change which adds functionality)
• Documentation update

How Has This Been Tested?

• Test Script (please provide)

import os

from embedchain import App

os.environ["PINECONE_API_KEY"] = "xxx"

config = {
    "vectordb": {
        "provider": "pinecone",
        "config": {
            "metric": "dotproduct",
            "vector_dimension": 1536,
            "index_name": "ec-test",
            "serverless_config": {"cloud": "aws", "region": "us-west-2"},
        },
    }
}

app = App.from_config(config=config)

app.add("https://www.forbes.com/profile/bill-gates", metadata={"type": "forbes", "person": "gates", "year": 2022})
app.add("https://en.wikipedia.org/wiki/Bill_Gates", metadata={"type": "wiki", "person": "gates", "year": 2024})
app.add("https://www.forbes.com/profile/elon-musk", metadata={"type": "forbes", "person": "elon", "year": 2024})
app.add("https://en.wikipedia.org/wiki/Elon_Musk", metadata={"type": "wiki", "person": "elon", "year": 2022})

print("Filter with person: gates")
results = app.search("What is the net worth of Bill Gates?", where={"person": "gates"})
print("Num of search results: ", len(results))


print("Filter with person: elon and type: forbes")
results = app.search("What is the net worth of Bill Gates?", where={"person": "elon", "type": "forbes"})
print("Num of search results: ", len(results))


print("Filter with person: elon and year > 2023")
results = app.search(
    "What is the net worth of Elon Musk?", raw_filter={"$and": [{"person": "elon"}, {"year": {"$gt": 2023}}]}
)
print("Num of search results: ", len(results))

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