MB-59846, MB-59616, MB-61009: Cluster version tracking for features

+ Cluster version tracking for features:
    - xattrs
    - vector_base64
    - dims:4096
+ This change separates out feature strings for xattrs and vector_base64
  because xattrs is not restricted to vectors alone.
+ vector_base64 is combined with dims:4096 which are meant to go out
  together in v2 (7.6.2).
+ Also requires: blevesearch/bleve#2015

Change-Id: I44daa225b5c397e9f8cae26ce3fcb36cab9b26d6
Reviewed-on: https://review.couchbase.org/c/cbft/+/208927
Well-Formed: Build Bot <[email protected]>
Well-Formed: Restriction Checker
Reviewed-by: Likith B <[email protected]>
Tested-by: Abhi Dangeti <[email protected]>

cmd/cbft/main.go

@@ -343,7 +343,7 @@ func mainStart(cfg cbgt.Cfg, uuid string, tags []string, container string,
 		"," + cbft.FeatureFileTransferRebalance +
 		"," + cbft.FeatureGeoSpatial +
 		cbft.FeatureVectorSearchSupport() +
-		"," + cbft.FeatureXattrsAndBase64
+		"," + cbft.FeatureXattrs
 
 	extrasMap["version-cbft.app"] = version
 	extrasMap["version-cbft.lib"] = cbft.VERSION

knn_nosup.go

@@ -17,10 +17,16 @@ import (
 	"github.com/blevesearch/bleve/v2"
 )
 
+const featuresVectorBase64Dims4096 = ""
+
 func FeatureVectorSearchSupport() string {
 	return ""
 }
 
+func featureFlagForDims(int) string {
+	return ""
+}
+
 func interpretKNNForRequest(knn, knnOperator json.RawMessage, r *bleve.SearchRequest) (
 	*bleve.SearchRequest, error) {
 	// Not supported

knn_sup.go

@@ -17,8 +17,26 @@ import (
 	"github.com/blevesearch/bleve/v2"
 )
 
+// v2: 7.6.2
+const featuresVectorBase64Dims4096 = "vector_base64_dims:4096"
+
 func FeatureVectorSearchSupport() string {
-	return "," + FeatureVectorSearch
+	return "," + featureVectorSearch +
+		"," + featuresVectorBase64Dims4096
+}
+
+// method will return appropriate flag to check cluster wide
+// if & when dims' ceiling is raised in the future
+func featureFlagForDims(dims int) string {
+	if dims <= 2048 {
+		return ""
+	}
+
+	if dims <= 4096 {
+		return featuresVectorBase64Dims4096
+	}
+
+	return ""
 }
 
 func interpretKNNForRequest(knn, knnOperator json.RawMessage, r *bleve.SearchRequest) (