Deprecates Version field on BuildPlanRequirement and BuildpackPlanEntry

These fields were deprecated as part of Buildpack Spec RFC0043.
All buildpacks that make use of these fields should instead switch to
using the Metadata field to store/retrieve version information.
This field will be removed at some point in the future.

build.go

@@ -134,11 +134,13 @@ type BuildpackPlanEntry struct {
 
 	// Version if the version contraint that defines what would be an acceptable
 	// dependency provided by the buildpack.
+	//
+	// Deprecated: Retrieve version information from Metadata instead.
 	Version string `toml:"version"`
 
 	// Metadata is an unspecified field allowing buildpacks to communicate extra
 	// details about their requirement. Examples of this type of metadata might
-	// include details about what source was used to decide the Version
+	// include details about what source was used to decide the version
 	// constraint for a requirement.
 	Metadata map[string]interface{} `toml:"metadata"`
 }

detect.go

@@ -76,11 +76,13 @@ type BuildPlanRequirement struct {
 
 	// Version allows a requirement to include a constraint describing what
 	// versions of the dependency are considered acceptable.
+	//
+	// Deprecated: Store version information in Metadata instead.
 	Version string `toml:"version"`
 
 	// Metadata is an unspecified field allowing buildpacks to communicate extra
 	// details about their requirement. Examples of this type of metadata might
-	// include details about what source was used to decide the Version
+	// include details about what source was used to decide the version
 	// constraint for a requirement.
 	Metadata interface{} `toml:"metadata"`
 }