MB-27696: Allow a unique ID to be set for a Search Request (#1858)

Add a unique ID for a bleve Search Request which will be echo'd back in
the Search Result. Would be useful in a parallel search query scenario
to differentiate between the queries.

---------

Co-authored-by: Abhi Dangeti <[email protected]>

search.go

@@ -305,6 +305,7 @@ func (h *HighlightRequest) AddField(field string) {
 //
 // A special field named "*" can be used to return all fields.
 type SearchRequest struct {
+	ClientContextID  string            `json:"client_context_id,omitempty"`
 	Query            query.Query       `json:"query"`
 	Size             int               `json:"size"`
 	From             int               `json:"from"`
@@ -321,6 +322,10 @@ type SearchRequest struct {
 	sortFunc func(sort.Interface)
 }
 
+func (r *SearchRequest) SetClientContextID(id string) {
+	r.ClientContextID = id
+}
+
 func (r *SearchRequest) Validate() error {
 	if srq, ok := r.Query.(query.ValidatableQuery); ok {
 		if err := srq.Validate(); err != nil {
@@ -392,6 +397,7 @@ func (r *SearchRequest) SetSearchBefore(before []string) {
 func (r *SearchRequest) UnmarshalJSON(input []byte) error {
 	var (
 		temp struct {
+			ClientContextID  string            `json:"client_context_id"`
 			Q                json.RawMessage   `json:"query"`
 			Size             *int              `json:"size"`
 			From             int               `json:"from"`
@@ -424,6 +430,7 @@ func (r *SearchRequest) UnmarshalJSON(input []byte) error {
 			return err
 		}
 	}
+	r.ClientContextID = temp.ClientContextID
 	r.From = temp.From
 	r.Explain = temp.Explain
 	r.Highlight = temp.Highlight