[configuration] Specify YAML schema that configuration files should follow

[mx-psi]

Fixes #3962

Changes

Specifies the YAML schema to follow. A schema is a set of YAML tags (i.e. types) and a way to assign types.

YAML 1.2 recommends the 'Core schema': the types are those of JSON. Scalars are resolved as one would expect, see here for the details.

One important difference with the way that YAML 1.1 used to work is that integer scalars starting with a 0 are interpreted as being written in decimal notation; e.g. 0123 parses to the integer 123 instead of the integer 83 (you can still use octal notation in YAML 1.2 by using 0o123). Some YAML parsers deviate from the core schema in how this works, for example, both of the more commonly used YAML parsing libraries in Golang parse 0123 as 83 (go-yaml/yaml and goccy/go-yaml). This may make it a bit difficult to strictly follow this requirement in some languages.

For non-trivial changes, follow the change proposal process.

• Related issues Define or recommend YAML schema supported #3962, part of Alignment with OpenTelemetry Collector configuration #3963

[mx-psi]

cc @open-telemetry/configuration-maintainers

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 7 days.

[codeboten]

Thanks for following up on this @mx-psi!

[jack-berg]

@MrAlias and maybe @carlosalberto take a look when you can. I think this should be ready with an additional approval.