Restructure and enhance docs

[swallez]

This PR restructures the existing docs in separate pages and adds a number of tutorial pages for the most common or less obvious activities.

This isn't complete and more docs will follow, starting with complex aggregations and index mapping definitions.

[github-actions]

The backport to 7.17 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-7.17 7.17
# Navigate to the new working tree
cd .worktrees/backport-7.17
# Create a new branch
git switch --create backport-243-to-7.17
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick --mainline 1 0c10f1893f3e2db71707cdd61c1f8beaf501ff38
# Push it to GitHub
git push --set-upstream origin backport-243-to-7.17
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-7.17

Then, create a pull request where the base branch is 7.17 and the compare/head branch is backport-243-to-7.17.

[github-actions]

The backport to 8.1 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-8.1 8.1
# Navigate to the new working tree
cd .worktrees/backport-8.1
# Create a new branch
git switch --create backport-243-to-8.1
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick --mainline 1 0c10f1893f3e2db71707cdd61c1f8beaf501ff38
# Push it to GitHub
git push --set-upstream origin backport-243-to-8.1
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-8.1

Then, create a pull request where the base branch is 8.1 and the compare/head branch is backport-243-to-8.1.

[github-actions]

The backport to 8.2 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-8.2 8.2
# Navigate to the new working tree
cd .worktrees/backport-8.2
# Create a new branch
git switch --create backport-243-to-8.2
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick --mainline 1 0c10f1893f3e2db71707cdd61c1f8beaf501ff38
# Push it to GitHub
git push --set-upstream origin backport-243-to-8.2
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-8.2

Then, create a pull request where the base branch is 8.2 and the compare/head branch is backport-243-to-8.2.