feat: api versioning

This commit adds versioning to our API endpoints, with the current
version as `v1`. Under this scheme, each API version lives under
separate packages and is served under separate top-level prefixes, e.g.
`/v1` for the current version.

This necessitated a small refactor to make it easier to modularize the
initialization logic.

NOTE: you will need to update your restish configuration to add the
`/v1` prefix to each server. See the development doc diffs for more
details. Remember to run `restish api control-plane-local-<1,2,3> sync`
after updating the restish config.

PLAT-86

Author: jason-lynch

api/Makefile

@@ -1,5 +1,8 @@
 include ../tools.mk
 
+.PHONY: generate-v1
+generate-v1:
+	goa gen github.com/pgEdge/control-plane/api/v1/design -o v1
+
 .PHONY: generate
-generate:
-	goa gen github.com/pgEdge/control-plane/api/design
+generate: generate-v1

api/gen/http/openapi.json

@@ -5,18 +5,17 @@ import (
 	"net/http"
 
 	g "goa.design/goa/v3/dsl"
-)
 
-//go:embed version.txt
-var version string
+	"github.com/pgEdge/control-plane/api"
+)
 
 var _ = g.API("control-plane", func() {
-	g.Title("pgEdge Control Plane API")
-	g.Version(version)
+	g.Title("pgEdge Control Plane v1 API")
+	g.Version(api.Version)
 	g.Description("Service for creating, modifying, and operating pgEdge databases.")
 	g.Server("control-plane", func() {
 		g.Host("localhost", func() {
-			g.URI("http://localhost:3000")
+			g.URI("http://localhost:3000/v1")
 		})
 	})
 	g.Meta("openapi:operationId", "{method}")