[Config] Rework the main 'Configuration' topic

[andreyaksenov]

Related doc issue(s): #4190

Product: Tarantool
Since: 3.0/3.1
Root document: https://www.tarantool.io/en/doc/latest/concepts/configuration/
SME: @ Totktonada

Details

Below are some things that can be improved:

• Remove the Configuration options overview section after fixing [Config] Document 'memtx' configuration settings #4012.
• Update the structure of the Configuration section:
  • Cluster configuration
    • Centralized configuration storages
    • Configuration in code (legacy)
• Emphasize the difference between two configuration approaches: in a file and config storage. For example, the diagrams from this topic can be moved to the main topic.
• Describe some examples of maintaining consistency in a file config: network folder, external tools for delivering the config file to different machines.
• Consider adding diagrams that help a reader understand main concepts, for example:
  • Config and one instance
  • Config and several instances on one machine
  • Config and several instances on different machines
  • Other ideas: Create a diagram that reflects how a cluster's configuration is applied to instances #3849 (comment)
• Add information about the config module API: [Config] Document the config module API #3662.
• Take Roles into account: Roles #3702.

Possible topic structure

• Configuration sources
  • Local
  • Сentralized
    Env vars.
• Configuring a cluster topology
  • Instance
  • Replica set
  • Group
  • Global
  • Scopes (merging)
• Developing applications
  • app/app_cfg
  • roles/roles_cfg
• Configuration values
  • Value type (string, number, array, dynamic (sync quorum), ...)
  • Default values
  • Predefined variables
• Environment variables
• Loading config from external storage (config.context)
• Configuration precedence
• Reloading configuration