Add HashiCorp Nomad provider (#483)

* provider: adding Nomad provider

* updating CONTRIBUTING.md with Nomad provider

* updated README.md by adding the Nomad provider

* fix typo

* adding nomad/api and nomad/testutil deps

* adding Nomad binary dependency for provider tests

* fixed the nomad binary download command step and added tolerations to the nomad provider.

* adding nomad provider demo gif

* adding my name to authors

* adding two missing go-rootcerts files after dep ensure

* delete pod comment

vendor/github.com/hashicorp/raft/peersjson.go

@@ -0,0 +1,98 @@
+package raft
+
+import (
+	"bytes"
+	"encoding/json"
+	"io/ioutil"
+)
+
+// ReadPeersJSON consumes a legacy peers.json file in the format of the old JSON
+// peer store and creates a new-style configuration structure. This can be used
+// to migrate this data or perform manual recovery when running protocol versions
+// that can interoperate with older, unversioned Raft servers. This should not be
+// used once server IDs are in use, because the old peers.json file didn't have
+// support for these, nor non-voter suffrage types.
+func ReadPeersJSON(path string) (Configuration, error) {
+	// Read in the file.
+	buf, err := ioutil.ReadFile(path)
+	if err != nil {
+		return Configuration{}, err
+	}
+
+	// Parse it as JSON.
+	var peers []string
+	dec := json.NewDecoder(bytes.NewReader(buf))
+	if err := dec.Decode(&peers); err != nil {
+		return Configuration{}, err
+	}
+
+	// Map it into the new-style configuration structure. We can only specify
+	// voter roles here, and the ID has to be the same as the address.
+	var configuration Configuration
+	for _, peer := range peers {
+		server := Server{
+			Suffrage: Voter,
+			ID:       ServerID(peer),
+			Address:  ServerAddress(peer),
+		}
+		configuration.Servers = append(configuration.Servers, server)
+	}
+
+	// We should only ingest valid configurations.
+	if err := checkConfiguration(configuration); err != nil {
+		return Configuration{}, err
+	}
+	return configuration, nil
+}
+
+// configEntry is used when decoding a new-style peers.json.
+type configEntry struct {
+	// ID is the ID of the server (a UUID, usually).
+	ID ServerID `json:"id"`
+
+	// Address is the host:port of the server.
+	Address ServerAddress `json:"address"`
+
+	// NonVoter controls the suffrage. We choose this sense so people
+	// can leave this out and get a Voter by default.
+	NonVoter bool `json:"non_voter"`
+}
+
+// ReadConfigJSON reads a new-style peers.json and returns a configuration
+// structure. This can be used to perform manual recovery when running protocol
+// versions that use server IDs.
+func ReadConfigJSON(path string) (Configuration, error) {
+	// Read in the file.
+	buf, err := ioutil.ReadFile(path)
+	if err != nil {
+		return Configuration{}, err
+	}
+
+	// Parse it as JSON.
+	var peers []configEntry
+	dec := json.NewDecoder(bytes.NewReader(buf))
+	if err := dec.Decode(&peers); err != nil {
+		return Configuration{}, err
+	}
+
+	// Map it into the new-style configuration structure.
+	var configuration Configuration
+	for _, peer := range peers {
+		suffrage := Voter
+		if peer.NonVoter {
+			suffrage = Nonvoter
+		}
+		server := Server{
+			Suffrage: suffrage,
+			ID:       peer.ID,
+			Address:  peer.Address,
+		}
+		configuration.Servers = append(configuration.Servers, server)
+	}
+
+	// We should only ingest valid configurations.
+	if err := checkConfiguration(configuration); err != nil {
+		return Configuration{}, err
+	}
+	return configuration, nil
+}