cookies: is &mut self required?

[secretfader]

&mut self doesn't seem to be required, as mentioned in #316.

Description

Change cookie trait function signature on get_cookie from &mut self to &self.

Motivation and Context

Tide seems to compile fine without requiring a mutable reference. Unsure why the previous behavior may have been required, but I believe there's little need to require mutability when reading cookie values.

How Has This Been Tested?

Existing tests passed.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[kamyuentse]

I think we should keep&mut self for set|remove_cookie.

[secretfader]

Ping @rustasync/maintainers

[secretfader]

This would be a breaking change, but I agree with the assertion in #316: that &mut self doesn't make sense here.

[secretfader]

I'm slightly concerned with merging this breaking API change, even though I believe it to be technically more correct. As a consumer of Tide and owner of several applications that will be broken when this change is released, and believe the update is worth applying.

I'll go ahead and merge since I'm no longer the only one frustrated (see #316, where the concern is similar to mine: building authentication middleware). Feel free to comment (or revert) if you feel strongly about requiring mut. I think dropping the requirement will make extracting data much cleaner.