Add support for optional connections

[patrick91]

Closes #3703

[sourcery-ai]

Reviewer's Guide by Sourcery

This PR adds support for nullable (optional) Connection types in Strawberry's relay field decorator. The implementation modifies the type handling in the relay fields to properly handle Optional Connection types and includes test cases to verify the functionality.

Class diagram for updated relay field decorator

classDiagram
    class StrawberryField {
        +apply(field: StrawberryField) void
        +resolve() void
        +connection_type: Type[Connection[Node]]
    }
    class Connection {
        <<interface>>
    }
    class Node {
        <<interface>>
    }
    class StrawberryOptional {
        +of_type: Type
    }
    class ConnectionGraphQLType {
        <<alias>>
    }
    StrawberryField --> Connection
    StrawberryField --> Node
    StrawberryField --> StrawberryOptional
    StrawberryField --> ConnectionGraphQLType
    note for ConnectionGraphQLType "Alias for handling optional Connection types"

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Class diagram for new test cases

classDiagram
    class User {
        +id: NodeID
        +name: str
        +resolve_nodes(info, node_ids, required) List[User]
    }
    class UserConnection {
        +resolve_connection(nodes: Iterable[User], info, after, before, first, last) Optional[Self]
    }
    class TestPermission {
        +message: str
        +has_permission(source, info, **kwargs) bool
    }
    UserConnection --> User
    TestPermission --> UserConnection
    note for User "Represents a user node in the relay connection"
    note for UserConnection "Handles the connection logic for User nodes"
    note for TestPermission "Custom permission class for testing"

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File-Level Changes

Change	Details	Files
Added support for nullable Connection types in the relay field decorator	Modified type checking to handle StrawberryOptional types Updated connection type casting to use the inner type for optional connections Changed ConnectionGraphQLType from Type[Connection[NodeType]] to Any to support optional types Added handling for union types in resolver type checking	strawberry/relay/fields.py
Fixed a typo in the optional type creation documentation	Corrected 'di' to 'do' in comment about Union type behavior	strawberry/annotation.py
Added comprehensive tests for nullable connections	Added test for nullable connection with Optional type Added test for nullable connection with pipe syntax (Python 3.10+) Added test for nullable connection with permissions	tests/relay/test_connection.py

Possibly linked issues

• Support for nullable Connection #3703: The PR implements nullable connection support, directly addressing the issue's request for this feature.

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[codspeed-hq]

CodSpeed Performance Report

Merging #3707 will not alter performance

_{Comparing fix-3703 (1b82b34) with main (069fe2c)}

Summary

✅ 15 untouched benchmarks

[codecov]

Codecov Report

Attention: Patch coverage is 96.96970% with 2 lines in your changes missing coverage. Please review.

Project coverage is 63.13%. Comparing base (069fe2c) to head (1b82b34).

❗ There is a different number of reports uploaded between BASE (069fe2c) and HEAD (1b82b34). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (069fe2c)	HEAD (1b82b34)
	2	1

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #3707       +/-   ##
===========================================
- Coverage   96.70%   63.13%   -33.58%     
===========================================
  Files         500      496        -4     
  Lines       33438    32339     -1099     
  Branches     5590     1663     -3927     
===========================================
- Hits        32336    20417    -11919     
- Misses        882    11589    +10707     
- Partials      220      333      +113     

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