Load core faasd service definitions from compose

**What**
- Use the compose-go library to read the service definitions from an
  external compose file instead of building them in Go
- Add default compose file and copy during `faasd install`
- Add test for load and parse of compose file
- Make testing easier  by sorting the env keys
- Allow append to instantiate the slices so that we can more easily test
  for proper parsing (e.g. nil is still nil etc)
- Add the arch suffix to the compose file and set this as part of the
  env when we parse the compose file. This allows faasd to dynamically
  set the arch suffix used for the basic auth and the gateway images.

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

vendor/github.com/xeipuuv/gojsonschema/schemaLoader.go

@@ -0,0 +1,206 @@
+// Copyright 2018 johandorland ( https://github.com/johandorland )
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package gojsonschema
+
+import (
+	"bytes"
+	"errors"
+
+	"github.com/xeipuuv/gojsonreference"
+)
+
+// SchemaLoader is used to load schemas
+type SchemaLoader struct {
+	pool       *schemaPool
+	AutoDetect bool
+	Validate   bool
+	Draft      Draft
+}
+
+// NewSchemaLoader creates a new NewSchemaLoader
+func NewSchemaLoader() *SchemaLoader {
+
+	ps := &SchemaLoader{
+		pool: &schemaPool{
+			schemaPoolDocuments: make(map[string]*schemaPoolDocument),
+		},
+		AutoDetect: true,
+		Validate:   false,
+		Draft:      Hybrid,
+	}
+	ps.pool.autoDetect = &ps.AutoDetect
+
+	return ps
+}
+
+func (sl *SchemaLoader) validateMetaschema(documentNode interface{}) error {
+
+	var (
+		schema string
+		err    error
+	)
+	if sl.AutoDetect {
+		schema, _, err = parseSchemaURL(documentNode)
+		if err != nil {
+			return err
+		}
+	}
+
+	// If no explicit "$schema" is used, use the default metaschema associated with the draft used
+	if schema == "" {
+		if sl.Draft == Hybrid {
+			return nil
+		}
+		schema = drafts.GetSchemaURL(sl.Draft)
+	}
+
+	//Disable validation when loading the metaschema to prevent an infinite recursive loop
+	sl.Validate = false
+
+	metaSchema, err := sl.Compile(NewReferenceLoader(schema))
+
+	if err != nil {
+		return err
+	}
+
+	sl.Validate = true
+
+	result := metaSchema.validateDocument(documentNode)
+
+	if !result.Valid() {
+		var res bytes.Buffer
+		for _, err := range result.Errors() {
+			res.WriteString(err.String())
+			res.WriteString("\n")
+		}
+		return errors.New(res.String())
+	}
+
+	return nil
+}
+
+// AddSchemas adds an arbritrary amount of schemas to the schema cache. As this function does not require
+// an explicit URL, every schema should contain an $id, so that it can be referenced by the main schema
+func (sl *SchemaLoader) AddSchemas(loaders ...JSONLoader) error {
+	emptyRef, _ := gojsonreference.NewJsonReference("")
+
+	for _, loader := range loaders {
+		doc, err := loader.LoadJSON()
+
+		if err != nil {
+			return err
+		}
+
+		if sl.Validate {
+			if err := sl.validateMetaschema(doc); err != nil {
+				return err
+			}
+		}
+
+		// Directly use the Recursive function, so that it get only added to the schema pool by $id
+		// and not by the ref of the document as it's empty
+		if err = sl.pool.parseReferences(doc, emptyRef, false); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+//AddSchema adds a schema under the provided URL to the schema cache
+func (sl *SchemaLoader) AddSchema(url string, loader JSONLoader) error {
+
+	ref, err := gojsonreference.NewJsonReference(url)
+
+	if err != nil {
+		return err
+	}
+
+	doc, err := loader.LoadJSON()
+
+	if err != nil {
+		return err
+	}
+
+	if sl.Validate {
+		if err := sl.validateMetaschema(doc); err != nil {
+			return err
+		}
+	}
+
+	return sl.pool.parseReferences(doc, ref, true)
+}
+
+// Compile loads and compiles a schema
+func (sl *SchemaLoader) Compile(rootSchema JSONLoader) (*Schema, error) {
+
+	ref, err := rootSchema.JsonReference()
+
+	if err != nil {
+		return nil, err
+	}
+
+	d := Schema{}
+	d.pool = sl.pool
+	d.pool.jsonLoaderFactory = rootSchema.LoaderFactory()
+	d.documentReference = ref
+	d.referencePool = newSchemaReferencePool()
+
+	var doc interface{}
+	if ref.String() != "" {
+		// Get document from schema pool
+		spd, err := d.pool.GetDocument(d.documentReference)
+		if err != nil {
+			return nil, err
+		}
+		doc = spd.Document
+	} else {
+		// Load JSON directly
+		doc, err = rootSchema.LoadJSON()
+		if err != nil {
+			return nil, err
+		}
+		// References need only be parsed if loading JSON directly
+		//  as pool.GetDocument already does this for us if loading by reference
+		err = sl.pool.parseReferences(doc, ref, true)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	if sl.Validate {
+		if err := sl.validateMetaschema(doc); err != nil {
+			return nil, err
+		}
+	}
+
+	draft := sl.Draft
+	if sl.AutoDetect {
+		_, detectedDraft, err := parseSchemaURL(doc)
+		if err != nil {
+			return nil, err
+		}
+		if detectedDraft != nil {
+			draft = *detectedDraft
+		}
+	}
+
+	err = d.parse(doc, draft)
+	if err != nil {
+		return nil, err
+	}
+
+	return &d, nil
+}