[bug] [refactoring] resolve optional dependency conflicts by refactoring __init__.py imports

[winiar93]

Problem

The current init.py contradicts the optional dependencies declared in pyproject.toml. Eager imports at module level force users to install all extra packages, making optional dependencies effectively mandatory.

TODO:

• standardize on absolute imports as recommended by pep8
• Reduce / restructure imports in init to avoud eager leading of optional extras
• define refactoring roadmap

acceptance criteria
Optinal dependencies declared in pyproject toml need to be truly optional - users who dont install extras shoudl not have an error.

[winiar93]

solution idea for imports in init.py

imports for sap

try:
    from .sap_bw import sap_bw_to_df
    from .sap_rfc import sap_rfc_to_df
except ImportError as e:
    raise ImportError("Install viadot2[sap]") from

for aws:

try:
    from .informix import informix_query, informix_to_df
    from .s3 import s3_upload_file
    from .redshift_spectrum import df_to_redshift_spectrum
    from .minio import df_to_minio
except ImportError as e:
    raise ImportError("Install viadot2[aws]") from e

[trymzet]

@winiar93 Yes, optional dependencies should escape the imports properly, this is described in the guide: https://viadot.docs.dyvenia.com/developer_guide/

One example implementing this is the SAP RFC source:
Source: https://github.com/dyvenia/viadot/blob/main/src/viadot/sources/sap_rfc.py#L19-L24
Task: https://github.com/dyvenia/viadot/blob/main/src/viadot/orchestration/prefect/tasks/sap_rfc.py#L11-L14
Tests: https://github.com/dyvenia/viadot/blob/main/tests/unit/test_sap_rfc.py#L10-L13