feat: Cache issues of fetched repositories

[ymtdzzz]

closes: #9

This PR provides the feature to cache issues of fetched repositories.

❯ make run-local-action
2025/03/20 16:24:31 Github client is initialized with given credentials
2025/03/20 16:24:31 
2025/03/20 16:24:31 >> Fetching issues for groupA <<
2025/03/20 16:24:31 Query: repo:open-telemetry/opentelemetry-ruby is:open is:issue label:"help wanted","good first issue","bug"
2025/03/20 16:24:31 Fetching page 1 ...
2025/03/20 16:24:32 
2025/03/20 16:24:32 >> Fetching issues for groupB <<
2025/03/20 16:24:32 Cache hit for open-telemetry/opentelemetry-ruby
2025/03/20 16:24:32 Query: repo:open-telemetry/opentelemetry-ruby-contrib is:open is:issue label:"help wanted","good first issue","bug"
2025/03/20 16:24:32 Fetching page 1 ...
2025/03/20 16:24:32 
2025/03/20 16:24:32 >> Fetching issues for groupC <<
2025/03/20 16:24:32 Cache hit for open-telemetry/opentelemetry-ruby
2025/03/20 16:24:32 Cache hit for open-telemetry/opentelemetry-ruby-contrib
2025/03/20 16:24:32 All issues are fetched from cache!
2025/03/20 16:24:32 Removing old issues directory: ./example/issues

[Copilot]

Pull Request Overview

This PR introduces caching for fetched repository issues to reduce redundant API calls. Key changes include:

• Adding a cache field to the client struct and updating related methods in pkg/client/client.go.
• Introducing a new test suite for the cache behavior in pkg/client/client_test.go.
• Updating repository identifiers in tests to match the cache key format.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
pkg/client/client.go	Added a cache field, updated NewClient and fetchIssuesByRepos logic to incorporate caching, and refined logging.
pkg/client/client_test.go	Added TestCheckCache and updated existing tests to use repository keys instead of full GitHub URLs.

Comments suppressed due to low confidence (2)

pkg/client/client.go:103

• [nitpick] Consider renaming the parameter 'ownerRepo' to something like 'repoKeys' for clearer intent.

func (c *client) checkCache(ownerRepo []string) ([]*github.Issue, []string) {

pkg/client/client_test.go:257

• [nitpick] Confirm that test inputs consistently use repository keys (e.g. 'owner/repo') as expected by the production code, given the change from full URLs.

ownerRepos: []string{"owner1/repo1", "owner2/repo2"},