Add embaas document extraction api endpoints (#6048)

# Introduces embaas document extraction api endpoints

In this PR, we add support for embaas document extraction endpoints to
Text Embedding Models (with LLMs, in different PRs coming). We currently
offer the MTEB leaderboard top performers, will continue to add top
embedding models and soon add support for customers to deploy thier own
models. Additional Documentation + Infomation can be found
[here](https://embaas.io).

While developing this integration, I closely followed the patterns
established by other langchain integrations. Nonetheless, if there are
any aspects that require adjustments or if there's a better way to
present a new integration, let me know! :)

Additionally, I fixed some docs in the embeddings integration.

Related PR: #5976 

#### Who can review?
  DataLoaders
  - @eyurtsev

tests/integration_tests/document_loaders/test_embaas.py

@@ -0,0 +1,59 @@
+from typing import Any
+from unittest.mock import MagicMock, patch
+
+import responses
+
+from langchain.document_loaders import EmbaasBlobLoader, EmbaasLoader
+from langchain.document_loaders.blob_loaders import Blob
+from langchain.document_loaders.embaas import EMBAAS_DOC_API_URL
+
+
+@responses.activate
+def test_handle_request() -> None:
+    responses.add(
+        responses.POST,
+        EMBAAS_DOC_API_URL,
+        json={
+            "data": {
+                "chunks": [
+                    {
+                        "text": "Hello",
+                        "metadata": {"start_page": 1, "end_page": 2},
+                        "embeddings": [0.0],
+                    }
+                ]
+            }
+        },
+        status=200,
+    )
+
+    loader = EmbaasBlobLoader(embaas_api_key="api_key", params={"should_embed": True})
+    documents = loader.parse(blob=Blob.from_data(data="Hello"))
+    assert len(documents) == 1
+    assert documents[0].page_content == "Hello"
+    assert documents[0].metadata["start_page"] == 1
+    assert documents[0].metadata["end_page"] == 2
+    assert documents[0].metadata["embeddings"] == [0.0]
+
+
+@responses.activate
+def test_handle_request_exception() -> None:
+    responses.add(
+        responses.POST,
+        EMBAAS_DOC_API_URL,
+        json={"message": "Invalid request"},
+        status=400,
+    )
+    loader = EmbaasBlobLoader(embaas_api_key="api_key")
+    try:
+        loader.parse(blob=Blob.from_data(data="Hello"))
+    except Exception as e:
+        assert "Invalid request" in str(e)
+
+
+@patch.object(EmbaasBlobLoader, "_handle_request")
+def test_load(mock_handle_request: Any) -> None:
+    mock_handle_request.return_value = [MagicMock()]
+    loader = EmbaasLoader(file_path="test_embaas.py", embaas_api_key="api_key")
+    documents = loader.load()
+    assert len(documents) == 1