add dashscope text embedding (#5929)

#### What I do
Adding embedding api for
[DashScope](https://help.aliyun.com/product/610100.html), which is the
DAMO Academy's multilingual text unified vector model based on the LLM
base. It caters to multiple mainstream languages worldwide and offers
high-quality vector services, helping developers quickly transform text
data into high-quality vector data. Currently supported languages
include Chinese, English, Spanish, French, Portuguese, Indonesian, and
more.

#### Who can review?

  Models
  - @hwchase17
  - @agola11

---------

Co-authored-by: Harrison Chase <hw.chase.17@gmail.com>

tests/integration_tests/embeddings/test_dashscope.py

@@ -0,0 +1,55 @@
+"""Test dashscope embeddings."""
+import numpy as np
+
+from langchain.embeddings.dashscope import DashScopeEmbeddings
+
+
+def test_dashscope_embedding_documents() -> None:
+    """Test dashscope embeddings."""
+    documents = ["foo bar"]
+    embedding = DashScopeEmbeddings(model="text-embedding-v1")
+    output = embedding.embed_documents(documents)
+    assert len(output) == 1
+    assert len(output[0]) == 1536
+
+
+def test_dashscope_embedding_documents_multiple() -> None:
+    """Test dashscope embeddings."""
+    documents = ["foo bar", "bar foo", "foo"]
+    embedding = DashScopeEmbeddings(model="text-embedding-v1")
+    output = embedding.embed_documents(documents)
+    assert len(output) == 3
+    assert len(output[0]) == 1536
+    assert len(output[1]) == 1536
+    assert len(output[2]) == 1536
+
+
+def test_dashscope_embedding_query() -> None:
+    """Test dashscope embeddings."""
+    document = "foo bar"
+    embedding = DashScopeEmbeddings(model="text-embedding-v1")
+    output = embedding.embed_query(document)
+    assert len(output) == 1536
+
+
+def test_dashscope_embedding_with_empty_string() -> None:
+    """Test dashscope embeddings with empty string."""
+    import dashscope
+
+    document = ["", "abc"]
+    embedding = DashScopeEmbeddings(model="text-embedding-v1")
+    output = embedding.embed_documents(document)
+    assert len(output) == 2
+    assert len(output[0]) == 1536
+    expected_output = dashscope.TextEmbedding.call(
+        input="", model="text-embedding-v1", text_type="document"
+    ).output["embeddings"][0]["embedding"]
+    assert np.allclose(output[0], expected_output)
+    assert len(output[1]) == 1536
+
+
+if __name__ == "__main__":
+    test_dashscope_embedding_documents()
+    test_dashscope_embedding_documents_multiple()
+    test_dashscope_embedding_query()
+    test_dashscope_embedding_with_empty_string()