Add rate limit cache and fixes

This change adds a loop that keeps a cache of credentials rate limits
as reported by the github API. The cache is updated every 30 seconds
and is purely informational for the user.

This change also adds some caching improvements. Functions that return
values from the cache as lists, will now sort by ID or creation date.

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

runner/github_credentials.go

@@ -7,6 +7,7 @@ import (
 
 	runnerErrors "github.com/cloudbase/garm-provider-common/errors"
 	"github.com/cloudbase/garm/auth"
+	"github.com/cloudbase/garm/cache"
 	"github.com/cloudbase/garm/params"
 )
 
@@ -15,11 +16,24 @@ func (r *Runner) ListCredentials(ctx context.Context) ([]params.GithubCredential
 		return nil, runnerErrors.ErrUnauthorized
 	}
 
+	// Get the credentials from the store. The cache is always updated after the database successfully
+	// commits the transaction that created/updated the credentials.
+	// If we create a set of credentials then immediately after we call ListCredentials,
+	// there is a posibillity that not all creds will be in the cache.
 	creds, err := r.store.ListGithubCredentials(ctx)
 	if err != nil {
 		return nil, errors.Wrap(err, "fetching github credentials")
 	}
 
+	// If we do have cache, update the rate limit for each credential. The rate limits are queried
+	// every 30 seconds and set in cache.
+	credsCache := cache.GetAllGithubCredentialsAsMap()
+	for idx, cred := range creds {
+		inCache, ok := credsCache[cred.ID]
+		if ok {
+			creds[idx].RateLimit = inCache.RateLimit
+		}
+	}
 	return creds, nil
 }
 
@@ -50,6 +64,11 @@ func (r *Runner) GetGithubCredentials(ctx context.Context, id uint) (params.Gith
 		return params.GithubCredentials{}, errors.Wrap(err, "failed to get github credentials")
 	}
 
+	cached, ok := cache.GetGithubCredentials((creds.ID))
+	if ok {
+		creds.RateLimit = cached.RateLimit
+	}
+
 	return creds, nil
 }