models - move abstract class

[pgrayy]

Description

For better code organization and clearer reporting of code paths in logs, moving the model abstract base class definition from types into the models subpackage. Additionally, I am removing the base openai model class in favor of deriving from the main openai model class when needed.

Related Issues

No formal issue opened.

Documentation PR

strands-agents/docs#128

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Other (please describe):

Testing

How have you tested the change? Verify that the changes do not break functionality or introduce warnings in consuming repositories: agents-docs, agents-tools, agents-cli

• I ran hatch run prepare
• Also ran the model integ tests.

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published

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