[chore] add a RFC to codify the work on JSON schema configuration support

docs/rfcs/component-schema.md

@@ -0,0 +1,93 @@
+# Component Schema
+
+## Overview
+
+OpenTelemetry components expose configuration as a public API.
+This public API is currently expressed directly in Golang structs.
+
+This RFC discusses expressing the public API of components as JSON schema files.
+
+## Past approaches
+
+### `configschema`
+The [`configschema`](https://pkg.go.dev/github.com/open-telemetry/opentelemetry-collector-contrib/cmd/configschema) go tool was part of opentelemetry-collector-contrib and used to build a specific YAML schema.
+
+It required to import all go modules as part of schemabuilder's dependencies, which created issues with the build of the repository.
+
+See https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/30187
+
+### Golang JSON schema reverse-engineering
+
+This approach consists of reverse-engineering the JSON schema from the Golang config structs.
+
+This approach ran into issues with the Golang generation from JSON schema.
+
+See https://github.com/open-telemetry/opentelemetry-collector-contrib/pull/27003 for historical context.
+
+### mdatagen Config struct generation
+
+This is [an in-progress approach](https://github.com/open-telemetry/opentelemetry-collector/pull/13155) where the metadata.yaml file of the component contains a config key, under which a JSON schema is present.
+
+This approach is demonstrated with a POC showing the batchprocessor configuration.
+
+Issues are present when it comes to composing configuration by embedding a library such as confighttp.
+
+### checkapi schema check
+
+This is an [in-progress approach](https://github.com/open-telemetry/opentelemetry-go-build-tools/pull/1148) where checkapi, a tool built as part of opentelemetry-go-build-tools, is used to check that
+the schema present under the config key of metadata.yaml matches the Config struct fields.
+
+This approach limits to the presence of fields in the Config struct.
+
+The tool can output the missing elements of the schema ; as such it can give a first take on the schema of the component.
+
+The tool also can associate imports such as confighttp.ClientConfig to a reference to a remote schema.
+
+## Goals
+
+We want to use JSON schema to help formulate and stabilize the public API of the components.
+
+JSON schema consumers use it to:
+* Create component configurations.
+* Validate component configurations.
+* Version the configuration of components.
+
+See https://github.com/open-telemetry/opentelemetry-collector/issues/9769 for discussion of the goals.
+
+See https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/42214 for a more recent discussion of goals and roadmap.
+
+## Current behavior
+
+### Validation via the `validate` command
+
+The collector can run with a validate CLI option that runs validation of the yaml file.
+
+### Configuration SIG
+
+There is a [SIG](https://github.com/open-telemetry/opentelemetry-configuration) dedicated to OpenTelemetry Configuration ; members of the SIG should review and sign off on this approach.
+
+## Roadmap
+
+To integrate JSON schema into components, we will need to make incremental changes with an opt-in approach.
+
+### Initial schemas
+
+We work to add initial schemas by hand in libraries in opentelemetry-collector.
+
+The schemas are added to the library metadata.yaml files.
+
+[A PR is open to implememt this.](https://github.com/open-telemetry/opentelemetry-collector/pull/13726)
+
+### CheckAPI - optional
+
+We upgrade checkapi to 0.27.1 and turn on schema validation in metadata.yaml if present.
+
+We add configuration in checkapi to add references to schemas defined in the previous step.
+
+### Add a schema to each component
+
+Create a schema for all components opting in, starting with simple components and adding more complex ones that provide validation of the approach.
+
+### Tie schema configuration to stability levels
+
+We add to the stability level requirements of the stable level the need to set a configuration schema for the component.