sequenceDiagram
    participant Client
    participant REST as REST Handler
    participant Filter as Field Filter
    participant HelmRelease as HelmRelease Lister
    participant Converter as Resource Converter

    Client->>REST: List Request (field selector)
    REST->>Filter: ParseFieldSelector()
    Filter-->>REST: Filter{Name, Namespace}
    
    REST->>REST: Check namespace match
    alt Namespace mismatch
        REST-->>Client: Empty List
    else Namespace matches
        REST->>HelmRelease: List with LabelSelector
        HelmRelease-->>REST: HelmRelease items
        
        loop For each HelmRelease
            REST->>Filter: MatchesName() + MatchesNamespace()
            Filter-->>REST: true/false
            alt Matches
                REST->>Converter: Convert to Resource
                Converter-->>REST: Resource
                REST->>REST: Add to results
            end
        end
        
        REST-->>Client: Filtered Resource List
    end

sequenceDiagram
    participant Client
    participant REST as REST Handler
    participant Filter as Field Filter
    participant Watcher as HelmRelease Watcher
    participant CustomWatcher as Custom Event Filter
    participant Converter as Resource Converter

    Client->>REST: Watch Request (field selector)
    REST->>Filter: ParseFieldSelector()
    Filter-->>REST: Filter{Name, Namespace}
    
    REST->>Watcher: Watch with LabelSelector
    Watcher-->>CustomWatcher: HelmRelease events
    
    loop For each event
        CustomWatcher->>Filter: MatchesName() + MatchesNamespace()
        Filter-->>CustomWatcher: true/false
        alt Matches
            CustomWatcher->>Converter: Convert to Resource event
            Converter-->>CustomWatcher: Resource event
            CustomWatcher-->>Client: Filtered event
        else No match
            CustomWatcher->>CustomWatcher: Filter out
        end
    end

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Summary of Changes

Hello @kvaps, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves an issue where kubectl field selector queries for custom resources like Applications, TenantModules, and TenantSecrets were not working as expected. The core problem stemmed from the controller-runtime cache's lack of native support for field selectors. The solution involves introducing a new, dedicated utility for parsing field selectors and then applying manual filtering for metadata.name and metadata.namespace after the initial data retrieval. This ensures that kubectl commands with these field selectors now correctly filter the results.

Highlights

• Centralized Field Selector Parsing: Introduced a new pkg/registry/fields package with a ParseFieldSelector utility to centralize and standardize the parsing of field selectors across different resource registries.
• Manual Field Selector Filtering: Implemented manual post-processing for metadata.name and metadata.namespace field selectors within the List() and Watch() methods for Application, TenantModule, and TenantSecret resources. This addresses the limitation where controller-runtime cache does not natively support field selectors.
• Refactored Client List Options: Removed the Raw field and direct FieldSelector usage from client.ListOptions when querying the underlying client, aligning with the manual filtering approach.
• Corrected kubectl Queries: Fixed the incorrect filtering behavior for kubectl queries using --field-selector=metadata.name or --field-selector=metadata.namespace for Application, TenantModule, and TenantSecret resources.

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