feat: refactor api spec to use OpenAPI and add missing spec

Convert the existing swagger2.0 file to a moden OpenAPI file.
Add missing endpoitns and model definitions.

Signed-off-by: Lucas Roesler <roesler.lucas@gmail.com>

gateway/models/model_prometheus_inner_alert.go

@@ -0,0 +1,48 @@
+// This file is auto-generated, DO NOT EDIT.
+//
+// Source:
+//
+//	Title: OpenFaaS API Gateway
+//	Version: 0.8.12
+package models
+
+import (
+	validation "github.com/go-ozzo/ozzo-validation/v4"
+)
+
+// PrometheusInnerAlert is an object. A single alert produced by Prometheus
+type PrometheusInnerAlert struct {
+	// Labels: A single label of a Prometheus alert
+	Labels PrometheusInnerAlertLabel `json:"labels" mapstructure:"labels"`
+	// Status: The status of the alert
+	Status string `json:"status" mapstructure:"status"`
+}
+
+// Validate implements basic validation for this model
+func (m PrometheusInnerAlert) Validate() error {
+	return validation.Errors{
+		"labels": validation.Validate(
+			m.Labels, validation.NotNil,
+		),
+	}.Filter()
+}
+
+// GetLabels returns the Labels property
+func (m PrometheusInnerAlert) GetLabels() PrometheusInnerAlertLabel {
+	return m.Labels
+}
+
+// SetLabels sets the Labels property
+func (m *PrometheusInnerAlert) SetLabels(val PrometheusInnerAlertLabel) {
+	m.Labels = val
+}
+
+// GetStatus returns the Status property
+func (m PrometheusInnerAlert) GetStatus() string {
+	return m.Status
+}
+
+// SetStatus sets the Status property
+func (m *PrometheusInnerAlert) SetStatus(val string) {
+	m.Status = val
+}