OpenAPI: update path separator

[swallez]

Follow-up to #4184 - using the : was wrong, as $ref paths must be RFC-3986 compliant, and : is a reserved char that must be escaped. Furthermore, identifiers in components are further restricted and must match ^[a-zA-Z0-9.-_]+$`

This PR also outputs example values as JSON when they can be successfully parsed instead of just outputting them as strings, as required by the spec Reverted, needs more work (json with multiline strings, ndjson, etc)

[swallez]

@lcawl I added you as reviewer: path separator has been updated again (for good this time). Shouldn't be an issue, but we'd better cross-check that it doesn't impact docs.

[lcawl]

LGTM

[github-actions]

The backport to 8.x failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-8.x 8.x
# Navigate to the new working tree
cd .worktrees/backport-8.x
# Create a new branch
git switch --create backport-4199-to-8.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 5db306e172f9a495f100a390b2cbc8c5b3733934
# Push it to GitHub
git push --set-upstream origin backport-4199-to-8.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-8.x

Then, create a pull request where the base branch is 8.x and the compare/head branch is backport-4199-to-8.x.

[github-actions]

The backport to 8.18 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-8.18 8.18
# Navigate to the new working tree
cd .worktrees/backport-8.18
# Create a new branch
git switch --create backport-4199-to-8.18
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 5db306e172f9a495f100a390b2cbc8c5b3733934
# Push it to GitHub
git push --set-upstream origin backport-4199-to-8.18
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-8.18

Then, create a pull request where the base branch is 8.18 and the compare/head branch is backport-4199-to-8.18.

[github-actions]

The backport to 9.0 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-9.0 9.0
# Navigate to the new working tree
cd .worktrees/backport-9.0
# Create a new branch
git switch --create backport-4199-to-9.0
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 5db306e172f9a495f100a390b2cbc8c5b3733934
# Push it to GitHub
git push --set-upstream origin backport-4199-to-9.0
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-9.0

Then, create a pull request where the base branch is 9.0 and the compare/head branch is backport-4199-to-9.0.