Update pkg/osv to allow overriding the http client / transport. (#357)

I don't know if you all intended `pkg/osv` to be a general purpose
https://osv.dev/ client library, but we are using it as that here:
https://github.com/guacsec/guac/blob/main/pkg/certifier/osv/osv.go

It would be nice to override the http client used to insert custom
transports, etc.

Signed-off-by: Jeff Mendoza <jlm@jlm.name>

pkg/osv/osv.go

@@ -127,6 +127,12 @@ func checkResponseError(resp *http.Response) error {
 
 // MakeRequest sends a batched query to osv.dev
 func MakeRequest(request BatchedQuery) (*BatchedResponse, error) {
+	return MakeRequestWithClient(request, http.DefaultClient)
+}
+
+// MakeRequestWithClient sends a batched query to osv.dev with the provided
+// http client.
+func MakeRequestWithClient(request BatchedQuery, client *http.Client) (*BatchedResponse, error) {
 	// API has a limit of 1000 bulk query per request
 	queryChunks := chunkBy(request.Queries, maxQueriesPerRequest)
 	var totalOsvResp BatchedResponse
@@ -140,7 +146,7 @@ func MakeRequest(request BatchedQuery) (*BatchedResponse, error) {
 		resp, err := makeRetryRequest(func() (*http.Response, error) {
 			// We do not need a specific context
 			//nolint:noctx
-			return http.Post(QueryEndpoint, "application/json", requestBuf)
+			return client.Post(QueryEndpoint, "application/json", requestBuf)
 		})
 		if err != nil {
 			return nil, err
@@ -166,9 +172,15 @@ func MakeRequest(request BatchedQuery) (*BatchedResponse, error) {
 
 // Get a Vulnerability for the given ID.
 func Get(id string) (*models.Vulnerability, error) {
+	return GetWithClient(id, http.DefaultClient)
+}
+
+// GetWithClient gets a Vulnerability for the given ID with the provided http
+// client.
+func GetWithClient(id string, client *http.Client) (*models.Vulnerability, error) {
 	resp, err := makeRetryRequest(func() (*http.Response, error) {
 		//nolint:noctx
-		return http.Get(GetEndpoint + "/" + id)
+		return client.Get(GetEndpoint + "/" + id)
 	})
 	if err != nil {
 		return nil, err
@@ -192,6 +204,12 @@ func Get(id string) (*models.Vulnerability, error) {
 // Hydrate fills the results of the batched response with the full
 // Vulnerability details.
 func Hydrate(resp *BatchedResponse) (*HydratedBatchedResponse, error) {
+	return HydrateWithClient(resp, http.DefaultClient)
+}
+
+// HydrateWithClient fills the results of the batched response with the full
+// Vulnerability details using the provided http client.
+func HydrateWithClient(resp *BatchedResponse, client *http.Client) (*HydratedBatchedResponse, error) {
 	hydrated := HydratedBatchedResponse{}
 	ctx := context.TODO()
 	// Preallocate the array to avoid slice reallocations when inserting later
@@ -211,7 +229,7 @@ func Hydrate(resp *BatchedResponse) (*HydratedBatchedResponse, error) {
 			}
 
 			go func(id string, batchIdx int, resultIdx int) {
-				vuln, err := Get(id)
+				vuln, err := GetWithClient(id, client)
 				if err != nil {
 					errChan <- err
 				} else {