fix: weaviate handles lowercase index names

[jupyterjazz]

WeaviateDocumentIndex capitalizes the index name when creating an index, so if we pass lowercase index name, there's a mismatch leading to various errors

from docarray import BaseDoc, DocList
from docarray.index import WeaviateDocumentIndex
from docarray.typing import NdArray
from pydantic import Field
import numpy as np

# Define the document schema.
class MyDoc(BaseDoc):
    title: str
    embedding: NdArray[128] = Field(is_embedding=True)

# Create dummy documents.
docs = DocList[MyDoc](MyDoc(title=f'title #{i}', embedding=np.random.rand(128)) for i in range(10))

# Initialize a new WeaviateDocumentIndex instance and add the documents to the index.
doc_index = WeaviateDocumentIndex[MyDoc](index_name='zdzd')
doc_index.index(docs)

# Perform a vector search.
query = np.ones(128)
retrieved_docs = doc_index.find(query, limit=10)

File "/Users/jinaai/Desktop/docarray/docarray/index/backends/weaviate.py", line 354, in find
docs, scores = self._find(
File "/Users/jinaai/Desktop/docarray/docarray/index/backends/weaviate.py", line 408, in _find
results["data"]["Get"][index_name], score_name
KeyError: 'zdzd'

Solution: add a post_init function that capitalizes the first letter of the index name

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (b306c80) 85.51% compared to head (00147c6) 85.51%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1711   +/-   ##
=======================================
  Coverage   85.51%   85.51%           
=======================================
  Files         132      132           
  Lines        8303     8308    +5     
=======================================
+ Hits         7100     7105    +5     
  Misses       1203     1203           

Flag	Coverage Δ
docarray	85.51% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
docarray/index/backends/hnswlib.py	95.33% <100.00%> (+0.05%)	⬆️
docarray/index/backends/weaviate.py	95.04% <100.00%> (+0.02%)	⬆️

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[github-actions]

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