write documentation ?_returning filter parameter (query string)

[avelino]

we have the _returning filter (parameter) implemented, but it is not documented

• markdown file
• documentation topic

implementation code:

prest/adapters/postgres/postgres.go

Lines 282 to 296 in 3bcad82

	// ReturningByRequest create interface for queries + returning
	func (adapter *Postgres) ReturningByRequest(r *http.Request) (returningSyntax string, err error) {
	// TODO: write documentation:
	// https://docs.prestd.com/query-statements/#filters-parameters-query-string---get
	queries := r.URL.Query()["_returning"]
	if len(queries) > 0 {
	for i, q := range queries {
	if i > 0 && i < len(queries) {
	returningSyntax += ", "
	}
	returningSyntax += q
	}
	}
	return
	}