support for async call to repo sync using options pattern

[3choBoomer]

Summary

Adds support for triggering an asynchronous repository sync by introducing a functional options pattern on the existing RepoListSync method.

This is one of two proposed approaches to resolve #74, which has been open since 2024. See #XX for an alternative implementation that adds a dedicated RepoListSyncAsync() function instead.

Changes

• Adds RepoListSyncOption functional option type
• Adds WithRepoListSyncAsync() option constructor, which appends async=true to the request URL
• Updates RepoListSync in both the Client interface and client implementation to accept opts ...RepoListSyncOption

Usage

// Existing behaviour — unchanged
repos, err := client.RepoListSync()

// New — trigger async sync
repos, err := client.RepoListSync(drone.WithRepoListSyncAsync())

Notes

• This is backwards compatible — all existing callers of RepoListSync() continue to work without modification.
  • code that references an interface for this functionality may need minor code changes.

The functional options pattern also leaves room for future query parameters to be added without further signature changes.

Alternatives

See #76 for an alternative that adds a dedicated RepoListSyncAsync() function instead. That approach keeps the Client interface flat and makes the async behaviour self-documenting via the function name, at the cost of a new method per option.

[CLAassistant]

All committers have signed the CLA.

[3choBoomer]

Closing in favor of #76