(new): support Bot API 10.3

(fix): finalize v2 contracts
(tests): cover v2 migration
(doc): prepare release guidance

utils/version.go

@@ -2,13 +2,13 @@ package utils
 
 const (
 	// VersionString is the module version string.
-	VersionString = "1.2.0"
+	VersionString = "2.0.0-rc.1"
 	// VersionMajor is the module major version.
-	VersionMajor = 1
+	VersionMajor = 2
 	// VersionMinor is the module minor version.
-	VersionMinor = 2
+	VersionMinor = 0
 	// VersionPatch is the module patch version.
 	VersionPatch = 0
 	// VersionBeta is the prerelease counter for the current version.
-	VersionBeta = 0
+	VersionBeta = 1
 )