feat: async llm support

feat: introduce async contract to BaseLLM

feat: add async call support for:

Azure provider

Anthropic provider

OpenAI provider

Gemini provider

Bedrock provider

LiteLLM provider

chore: expand scrubbed header fields (conftest, anthropic, bedrock)

chore: update docs to cover async functionality

chore: update and harden tests to support acall; re-add uri for cassette compatibility

chore: generate missing cassette

fix: ensure acall is non-abstract and set supports_tools = true for supported Anthropic models

chore: improve Bedrock async docstring and general test robustness

lib/crewai/tests/llms/bedrock/test_bedrock_async.py

@@ -0,0 +1,127 @@
+"""Tests for Bedrock async completion functionality.
+
+Note: These tests are skipped in CI because VCR.py does not support
+aiobotocore's HTTP session. The cassettes were recorded locally but
+cannot be played back properly in CI.
+"""
+
+import pytest
+import tiktoken
+
+from crewai.llm import LLM
+
+SKIP_REASON = "VCR does not support aiobotocore async HTTP client"
+
+
+@pytest.mark.vcr()
+@pytest.mark.asyncio
+@pytest.mark.skip(reason=SKIP_REASON)
+async def test_bedrock_async_basic_call():
+    """Test basic async call with Bedrock."""
+    llm = LLM(model="bedrock/us.anthropic.claude-3-5-sonnet-20241022-v2:0")
+
+    result = await llm.acall("Say hello")
+
+    assert result is not None
+    assert isinstance(result, str)
+    assert len(result) > 0
+
+
+@pytest.mark.vcr()
+@pytest.mark.asyncio
+@pytest.mark.skip(reason=SKIP_REASON)
+async def test_bedrock_async_with_temperature():
+    """Test async call with temperature parameter."""
+    llm = LLM(model="bedrock/us.anthropic.claude-3-5-sonnet-20241022-v2:0", temperature=0.1)
+
+    result = await llm.acall("Say the word 'test' once")
+
+    assert result is not None
+    assert isinstance(result, str)
+
+
+@pytest.mark.vcr()
+@pytest.mark.asyncio
+@pytest.mark.skip(reason=SKIP_REASON)
+async def test_bedrock_async_with_max_tokens():
+    """Test async call with max_tokens parameter."""
+    llm = LLM(model="bedrock/us.anthropic.claude-3-5-sonnet-20241022-v2:0", max_tokens=10)
+
+    result = await llm.acall("Write a very long story about a dragon.")
+
+    assert result is not None
+    assert isinstance(result, str)
+    encoder = tiktoken.get_encoding("cl100k_base")
+    token_count = len(encoder.encode(result))
+    assert token_count <= 10
+
+
+@pytest.mark.vcr()
+@pytest.mark.asyncio
+@pytest.mark.skip(reason=SKIP_REASON)
+async def test_bedrock_async_with_system_message():
+    """Test async call with system message."""
+    llm = LLM(model="bedrock/us.anthropic.claude-3-5-sonnet-20241022-v2:0")
+
+    messages = [
+        {"role": "system", "content": "You are a helpful assistant."},
+        {"role": "user", "content": "What is 2+2?"}
+    ]
+
+    result = await llm.acall(messages)
+
+    assert result is not None
+    assert isinstance(result, str)
+
+
+@pytest.mark.vcr()
+@pytest.mark.asyncio
+@pytest.mark.skip(reason=SKIP_REASON)
+async def test_bedrock_async_conversation():
+    """Test async call with conversation history."""
+    llm = LLM(model="bedrock/us.anthropic.claude-3-5-sonnet-20241022-v2:0")
+
+    messages = [
+        {"role": "user", "content": "My name is Alice."},
+        {"role": "assistant", "content": "Hello Alice! Nice to meet you."},
+        {"role": "user", "content": "What is my name?"}
+    ]
+
+    result = await llm.acall(messages)
+
+    assert result is not None
+    assert isinstance(result, str)
+
+
+@pytest.mark.vcr()
+@pytest.mark.asyncio
+@pytest.mark.skip(reason=SKIP_REASON)
+async def test_bedrock_async_multiple_calls():
+    """Test making multiple async calls in sequence."""
+    llm = LLM(model="bedrock/us.anthropic.claude-3-5-sonnet-20241022-v2:0")
+
+    result1 = await llm.acall("What is 1+1?")
+    result2 = await llm.acall("What is 2+2?")
+
+    assert result1 is not None
+    assert result2 is not None
+    assert isinstance(result1, str)
+    assert isinstance(result2, str)
+
+
+@pytest.mark.vcr()
+@pytest.mark.asyncio
+@pytest.mark.skip(reason=SKIP_REASON)
+async def test_bedrock_async_with_parameters():
+    """Test async call with multiple parameters."""
+    llm = LLM(
+        model="bedrock/us.anthropic.claude-3-5-sonnet-20241022-v2:0",
+        temperature=0.7,
+        max_tokens=100,
+        top_p=0.9
+    )
+
+    result = await llm.acall("Tell me a short fact")
+
+    assert result is not None
+    assert isinstance(result, str)