[NOD-350] Implement testnet faucet (#438)

* [NOD-350] Implement testnet faucet

* [NOD-350] Add JSON annotations to api server response types

* [NOD-350] Fix IP check query, update IP usage with upsert, and make IP a primary key

* [NOD-377] Remove redundant float conversion

* [NOD-377] Change not current database error message

* [NOD-377] change API route from /money_request to /request_money

* [NOD-377] Add a constant for 24 hours

* [NOD-377] Remove redundant call for getWalletUTXOSet()

* [NOD-377] Condition refactoring

* [NOD-377] Fix POST request to API server content type

* [NOD-350] Rename day -> timeBetweenRequests

* [NOD-377] Rename timeBetweenRequests -> minRequestInterval, timeBefore24Hours -> minRequestInterval

* [NOD-350] Rename file responsetypes -> response_types

* [NOD-350] Rename convertTxModelToTxResponse -> convertTxDBModelToTxResponse

* [NOD-350] Explicitly select blue_score in fetchSelectedTipBlueScore

* [NOD-350] Refactor and add comments

* [NOD-350] Make calcFee use MassPerTxByte

* [NOD-350] Convert IP column to varchar(39) to allow ipv6 addresses

* [NOD-350] Add comments to isFundedAndIsChangeOutputRequired

* [NOD-350] Remove approximateConfirmationsForCoinbaseMaturity

* [NOD-350] Fix comments

httpserverutils/request.go

@@ -0,0 +1,58 @@
+package httpserverutils
+
+import (
+	"fmt"
+	"github.com/gorilla/mux"
+	"io/ioutil"
+	"net/http"
+)
+
+// HandlerFunc is a handler function that is passed to the
+// MakeHandler wrapper and gets the relevant request fields
+// from it.
+type HandlerFunc func(ctx *ServerContext, r *http.Request, routeParams map[string]string, queryParams map[string]string, requestBody []byte) (
+	interface{}, *HandlerError)
+
+// MakeHandler is a wrapper function that takes a handler in the form of HandlerFunc
+// and returns a function that can be used as a handler in mux.Router.HandleFunc.
+func MakeHandler(handler HandlerFunc) func(http.ResponseWriter, *http.Request) {
+	return func(w http.ResponseWriter, r *http.Request) {
+		ctx := ToServerContext(r.Context())
+
+		var requestBody []byte
+		if r.Method == "POST" {
+			var err error
+			requestBody, err = ioutil.ReadAll(r.Body)
+			if err != nil {
+				SendErr(ctx, w, NewInternalServerHandlerError("Error reading POST data"))
+			}
+		}
+
+		flattenedQueryParams, hErr := flattenQueryParams(r.URL.Query())
+		if hErr != nil {
+			SendErr(ctx, w, hErr)
+			return
+		}
+
+		response, hErr := handler(ctx, r, mux.Vars(r), flattenedQueryParams, requestBody)
+		if hErr != nil {
+			SendErr(ctx, w, hErr)
+			return
+		}
+		if response != nil {
+			SendJSONResponse(w, response)
+		}
+	}
+}
+
+func flattenQueryParams(queryParams map[string][]string) (map[string]string, *HandlerError) {
+	flattenedMap := make(map[string]string)
+	for param, valuesSlice := range queryParams {
+		if len(valuesSlice) > 1 {
+			return nil, NewHandlerError(http.StatusUnprocessableEntity, fmt.Sprintf("Couldn't parse the '%s' query parameter:"+
+				" expected a single value but got multiple values", param))
+		}
+		flattenedMap[param] = valuesSlice[0]
+	}
+	return flattenedMap, nil
+}