Add OCI recommended labels

Signed-off-by: Sambhav Kothari <[email protected]>

text/0000-annotations.md

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+# Meta
+[meta]: #meta
+- Name: OCI Image annotations
+- Start Date: 2021-12-03
+- Author(s): [@samj1912](https://github.com/samj1912)
+- Status: Draft <!-- Acceptable values: Draft, Approved, On Hold, Superseded -->
+- RFC Pull Request: (leave blank)
+- CNB Pull Request: (leave blank)
+- CNB Issue: (leave blank)
+- Supersedes: (put "N/A" unless this replaces an existing RFC, then link to that RFC)
+
+# Summary
+[summary]: #summary
+
+Add OCI recommended image labels to output images.
+
+# Definitions
+[definitions]: #definitions
+
+N/A
+
+# Motivation
+[motivation]: #motivation
+
+Certain OCI image scanning and debugging tools take into account standard labels on the images as defined by [OCI Spec - Pre-defined Annotation keys](https://github.com/opencontainers/image-spec/blob/main/annotations.md#pre-defined-annotation-keys). Buildpacks already records some of this information in the `project.toml` and other labels defined at https://github.com/buildpacks/spec/blob/main/platform.md#labels. We should also preserve this information in the output image in appropriate labels as recommended by the OCI spec.
+
+# What it is
+[what-it-is]: #what-it-is
+
+Adds OCI recommended labels to the output image.
+
+# How it Works
+[how-it-works]: #how-it-works
+
+Optionally adds the following labels where applicable - 
+
+- `org.opencontainers.image.base.name`: Run image tag name. Currently stored in `io.buildpacks.lifecycle.metadata.run-image.reference`
+- `org.opencontainers.image.base.digest`: Run image digest. Currently stored in `io.buildpacks.lifecycle.metadata.run-image.reference`
+
+The platform may also provide appropriate keys inside `project-metadata.toml` to the lifecycle so that it exports the appropriate labels listed below.
+
+- `org.opencontainers.image.source`: URL to the image source if the source is a source controlled repository, URL to a blob etc. Sourced from `source.metadata.repository`.
+- `org.opencontainers.image.revision`: Source controlled revision of application source code. Sourced from `source.version.commit`.
+- `org.opencontainers.image.authors`: Authors of hte image. Sourced from `source.metadata.authors`.
+- `org.opencontainers.image.version`: Authors of hte image. Sourced from `source.metadata.version`.
+- `org.opencontainers.image.documentation`: URL to find more information on the image. Sourced from `source.metadata.documentation-url`.
+- `org.opencontainers.image.title`: Human-readable title of the image. Sourced from `source.metadata.name`.
+- `org.opencontainers.image.licenses`: License(s) under which contained software is distributed as an SPDX License Expression. Sourced from `source.metadata.licenses`.
+
+A platform may choose to map the above fields to the fields defined in a project descriptor as noted at https://github.com/buildpacks/spec/blob/extensions/project-descriptor%2F0.2/extensions/project-descriptor.md#non-_-tables.
+
+Everything under `source.metadata.<key>` is mapped from `_.<key>` from the project descriptor in this case.
+
+# Drawbacks
+[drawbacks]: #drawbacks
+
+N/A
+
+# Alternatives
+[alternatives]: #alternatives
+
+N/A
+
+# Prior Art
+[prior-art]: #prior-art
+
+- https://github.com/buildpacks/rfcs/blob/main/text/0054-project-descriptor-schema.md
+- https://github.com/buildpacks/rfcs/blob/main/text/0084-project-descriptor-domains.md
+
+# Unresolved Questions
+[unresolved-questions]: #unresolved-questions
+
+N/A
+
+# Spec. Changes (OPTIONAL)
+[spec-changes]: #spec-changes
+
+Per above.