Document and test warning suppression for default CasbinRule table

[Copilot]

Users reported inability to suppress the RuntimeWarning when using the default CasbinRule table. The warning parameter existed but was undocumented, leading to confusion.

Changes

Warning message enhancement

• Updated RuntimeWarning text to explicitly mention suppression options (warning=False or db_class parameter)

Documentation

• Added "Suppressing the Default Table Warning" section to README with two approaches:

  # Option 1: warning parameter
  adapter = Adapter(engine, warning=False)
  
  # Option 2: explicit db_class
  adapter = Adapter(engine, db_class=CasbinRule)

Test coverage

• Added TestWarningParameter class with 5 tests covering:
  • Default warning behavior with updated message
  • Suppression via warning=False
  • Suppression via db_class=CasbinRule
  • Combined parameters
  • Custom db_class behavior

Original prompt

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This section details on the original issue you should resolve

<issue_title>Cant suppress warning</issue_title>
<issue_description>I don't know what has happened to the version in Pypi but it's not matching the version here.

I can't seem to suppress this warning

 RuntimeWarning: Using default CasbinRule table, please note the use of the 'Adapter().create_table()' method to create the table, and ignore this warning if you are using a custom CasbinRule table.

I tried passing db_class. Still got a warning. Setting warning=False, still got a warning. Both, still got a warning.

Checked the code that was downloaded from pypi. Doesn't have the warning param. </issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Cant suppress warning #17

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