Mulitple improvements of the crawler

1) Set document IDs to avoid duplicating documents;
2) Set the `creationTime` field of each document in the index;
3) set the `values`, `kinds` and `identifiers` fields for all documents;
4) Add a `Copy` method into the `Document` struct: this fixes the issue
where all the documents existing in the index point to the same Document
object;
5) Avoid using keystore redis;
6) Set imagePullPolicy to `Always` for crawler jobs.

api/internal/crawl/crawler/github/queries_test.go

@@ -68,7 +68,7 @@ func TestQueryType(t *testing.T) {
 
 func TestGithubSearchQuery(t *testing.T) {
 	const (
-		perPage     = 100
+		perPage = 100
 	)
 
 	testCases := []struct {
@@ -82,7 +82,7 @@ func TestGithubSearchQuery(t *testing.T) {
 	}{
 		{
 			rc: RequestConfig{
-				perPage:     perPage,
+				perPage: perPage,
 			},
 			codeQuery: Query{
 				Filename("kustomization.yaml"),