feat: add attachments support for coded conversational agents

[GabrielVasilescu04]

Development Package

• Use uipath pack --nolock to get the latest dev build from this PR (requires version range).
• Add this package as a dependency in your pyproject.toml:

[project]
dependencies = [
  # Exact version:
  "uipath-langchain==0.7.12.dev1006123161",

  # Any version from PR
  "uipath-langchain>=0.7.12.dev1006120000,<0.7.12.dev1006130000"
]

[[tool.uv.index]]
name = "testpypi"
url = "https://test.pypi.org/simple/"
publish-url = "https://test.pypi.org/legacy/"
explicit = true

[tool.uv.sources]
uipath-langchain = { index = "testpypi" }

[tool.uv]
override-dependencies = [
    "uipath-langchain>=0.7.12.dev1006120000,<0.7.12.dev1006130000",
]