Extract guides from "Behind the scenes" to

[bajtos]

At the moment, many pages in "Behind the scenes" are mixing explanations with how-to guides. This makes it difficult for our users to find the relevant content (a recipe to achieve the outcome they want).

As part of our adoption of the four-quadrant documentation system (see #5549 and #5718), we should extract all guides from explanation pages into guide pages (see #5768 for inspiration) and keep explanation pages focused on explaining the concepts & providing background information.

This story is a part of #5113 Documentation improvements 2020Q3.

List of pages to rework

• Application
• Server
• Controllers
• Models, especially "Defining a model at runtime"
• HasMany Relation
• BelongsTo Relation
• HasOne Relation
• DataSources
• Repositories
• Services
• Interceptors
• Life cycle observers
• Routes
• Sequence
• Routing requests
• Parsing requests
• Middleware
• Using Express Middleware
• Mixins
• Binding

[bajtos]

Closing as a duplicate of #5783

[bajtos]

duplicates #5783