Big refactor of generated code

- Stop generating helper functions for each model
- Move Insert/Update/Upsert query generation helpers to strmangle
- Add tests for query generation helpers
- Delete a lot of the Insert/Upsert tests that test the query generation
  helpers.
- Use tx for more of the tests.

strmangle/sets.go

@@ -1,5 +1,43 @@
 package strmangle
 
+// UpdateColumnSet generates the set of columns to update for an update statement.
+// if a whitelist is supplied, it's returned
+// if a whitelist is missing then we begin with all columns
+// then we remove the primary key columns
+func UpdateColumnSet(allColumns, pkeyCols, whitelist []string) []string {
+	if len(whitelist) != 0 {
+		return whitelist
+	}
+
+	return SetComplement(allColumns, pkeyCols)
+}
+
+// InsertColumnSet generates the set of columns to insert and return for an insert statement
+// the return columns are used to get values that are assigned within the database during the
+// insert to keep the struct in sync with what's in the db.
+// with a whitelist:
+// - the whitelist is used for the insert columns
+// - the return columns are the result of (columns with default values - the whitelist)
+// without a whitelist:
+// - start with columns without a default as these always need to be inserted
+// - add all columns that have a default in the database but that are non-zero in the struct
+// - the return columns are the result of (columns with default values - the previous set)
+func InsertColumnSet(cols, defaults, noDefaults, nonZeroDefaults, whitelist []string) ([]string, []string) {
+	if len(whitelist) > 0 {
+		return whitelist, SetComplement(defaults, whitelist)
+	}
+
+	var wl []string
+	wl = append(wl, noDefaults...)
+	wl = SetMerge(nonZeroDefaults, wl)
+	wl = SortByKeys(cols, wl)
+
+	// Only return the columns with default values that are not in the insert whitelist
+	rc := SetComplement(defaults, wl)
+
+	return wl, rc
+}
+
 // SetInclude checks to see if the string is found in the string slice
 func SetInclude(str string, slice []string) bool {
 	for _, s := range slice {