Support HTTP Basic authentication for OpenAPI tools

[aashnakunk]

Describe the Bug:
OpenAPI tools currently do not support HTTP Basic authentication. When an OpenAPI auth credential contains HTTP username/password credentials, ADK raises NotImplementedError("Basic Authentication is not supported.") instead of generating a standard Basic auth Authorization header.

Steps to Reproduce:

1. Use ADK OpenAPI tools with an OpenAPI security scheme that requires HTTP Basic auth.
2. Configure an AuthCredential with HTTP credentials containing username and/or password.
3. Run the OpenAPI tool auth helper path.
4. ADK raises:

NotImplementedError: Basic Authentication is not supported.
Expected Behavior:
ADK should support HTTP Basic auth for OpenAPI tools by generating an authorization header in the standard format:

text

Authorization: Basic base64(username:password)
Observed Behavior:
The current implementation explicitly raises NotImplementedError for HTTP credentials with username/password.

Relevant source location:

python

# src/google/adk/tools/openapi_tool/auth/auth_helpers.py
raise NotImplementedError("Basic Authentication is not supported.")
Environment Details:

ADK Library Version (pip show google-adk): main branch / current source checkout
Desktop OS: macOS
Python Version (python -V): N/A
Model Information:

Are you using LiteLLM: No
Which model is being used: N/A
🟡 Optional Information
Regression:
N/A

Logs:

text

NotImplementedError: Basic Authentication is not supported.
Screenshots / Video:
N/A

Additional Context:
HTTP Basic authentication is part of the OpenAPI HTTP security scheme family and is still used by some APIs. ADK already handles bearer-style HTTP credentials by generating an internal Authorization header. Basic auth could follow the same pattern, using Authorization: Basic <base64(username:password)>.

A possible implementation would:

Detect HTTP credentials with username/password.
Encode username:password with base64.
Return an internal Authorization header parameter and kwargs, similar to bearer token handling.
Add unit tests in tests/unittests/tools/openapi_tool/auth/test_auth_helper.py.
Minimal Reproduction Code:

python

# Conceptual repro based on current source behavior.
# The relevant code path is in:
# src/google/adk/tools/openapi_tool/auth/auth_helpers.py

# When auth_credential.auth_type == AuthCredentialTypes.HTTP
# and auth_credential.http.credentials.username/password are set,
# the helper currently raises:
# NotImplementedError("Basic Authentication is not supported.")


How often has this issue occurred?:

Always (100%)