authenticator storage engines

Created a storage interface used by authenticator to support multiple
types of storage types for private keys. Added a new file storage engine
which is now the default for web-api. Migrated aws secrets manager to be optional.

example-project/cmd/web-api/docs/docs.go

@@ -0,0 +1,80 @@
+// GENERATED BY THE COMMAND ABOVE; DO NOT EDIT
+// This file was generated by swaggo/swag at
+// 2019-06-24 15:42:25.999684 -0800 AKDT m=+0.030714022
+
+package docs
+
+import (
+	"bytes"
+
+	"github.com/alecthomas/template"
+	"github.com/swaggo/swag"
+)
+
+var doc = `{
+    "swagger": "2.0",
+    "info": {
+        "description": "This is a sample server celler server.",
+        "title": "SaaS Example API",
+        "termsOfService": "http://geeksinthewoods.com/terms",
+        "contact": {
+            "name": "API Support",
+            "url": "https://gitlab.com/geeks-accelerator/oss/saas-starter-kit",
+            "email": "support@geeksinthewoods.com"
+        },
+        "license": {
+            "name": "Apache 2.0",
+            "url": "http://www.apache.org/licenses/LICENSE-2.0.html"
+        },
+        "version": "{{.Version}}"
+    },
+    "host": "{{.Host}}",
+    "basePath": "{{.BasePath}}",
+    "paths": {},
+    "securityDefinitions": {
+        "ApiKeyAuth": {
+            "type": "apiKey",
+            "name": "Authorization",
+            "in": "header"
+        },
+        "BasicAuth": {
+            "type": "basic"
+        },
+        "OAuth2Password": {
+            "type": "oauth2",
+            "flow": "password",
+            "tokenUrl": "https://example.com/v1/oauth/token"
+        }
+    }
+}`
+
+type swaggerInfo struct {
+	Version     string
+	Host        string
+	BasePath    string
+	Title       string
+	Description string
+}
+
+// SwaggerInfo holds exported Swagger Info so clients can modify it
+var SwaggerInfo swaggerInfo
+
+type s struct{}
+
+func (s *s) ReadDoc() string {
+	t, err := template.New("swagger_info").Parse(doc)
+	if err != nil {
+		return doc
+	}
+
+	var tpl bytes.Buffer
+	if err := t.Execute(&tpl, SwaggerInfo); err != nil {
+		return doc
+	}
+
+	return tpl.String()
+}
+
+func init() {
+	swag.Register(swag.Name, &s{})
+}