fix: improve Lock.extend() and Lock.do_extend() return type to Literal[True]

[enioxt]

Description

Fixes #3792

This PR improves the type safety of and methods by changing their return type from to .

Problem

Currently, both methods are typed as returning , but in practice they only return or raise a exception. This can lead to developer confusion, as developers might write code like:

if not lock.extend(...):
    # This code will never run\!
    # Lock extension failures raise LockError instead

Solution

Changed return types to to clearly communicate that:

• These methods only return on success
• Failures are communicated via exception
• There's no meaningful conditional check on the return value

Changes

Sync version (redis/lock.py):

• extend(): bool → Literal[True]
• do_extend(): bool → Literal[True]

Async version (redis/asyncio/lock.py):

• extend(): Awaitable[bool] → Awaitable[Literal[True]]
• do_extend(): bool → Literal[True]

Testing

• Type-only change, no runtime behavior modified
• Existing tests continue to pass
• Improves type checking for users of these APIs

Benefits

• Better type safety: IDEs and type checkers can warn about pointless conditionals
• Clearer API: Developers immediately understand the exception-based error model
• Prevents bugs: Reduces likelihood of incorrect error handling code

Sacred Code: 000.111.369.963.1618

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[petyaslavova]

Hi @enioxt, thank you for your contribution! We will review your changes soon.

[petyaslavova]

Hi @enioxt, the changes look good!
I have just one request - to add in the docstrings info about the behavior. It will be a lot easier for the developers to gain orientation for the methods behavior.

   ```
    Returns:
        Literal[True]
            Short description when this value is returned....

    Raises:
        <Error Type>
            Short description when this error is raised