Add the ability to create subspace sections

[RiccardoM]

Feature description

Currently each subspace represents a single application within the Desmos ecosystem. As per ADR-010, each time a post is created it must be placed inside a subspace using its id as a reference. Although this works, it does not allow developers to create subspaces that need to represent complex systems just as forums. If a developer wanted to create a forum, they have to create different subspaces for each section, but this would result in having multiple user groups and permissions to be managed. Instead, I think it's worth introducing the idea of sections.

Implementation proposal

A subspace section defines a region within a subspace with its own rules. It can have its user groups and allows to store posts by referencing them though the section_id. A section can also have a parenting section so that sub-sections can be created to be able to build a forum or other complex social apps.

The basic idea of a section is the following:

// Section contains all the data of a subspace section
type Section struct {
  // Unique id of the section within the subspace (this is assigned upon the section creation)
  Id uint32 

  // Name of the section
  Name string

  // (optional) Description of the section
  Description string
  
  // (optional) Id of the parent section
  Parent uint32
}

Each subspace will have a default section with id 0 which represents the generic subspace itself.

Once sections are implemented, the following changes must be applied:

• permissions need to be checked against the (subspace_id, section_id) tuple instead of relying only on the subspace_id
• posts need to be stored within a specific section instead of a generic subspace

Note that by default sub-sections will inherit the permissions set on parent sections. Suppose the following sections are present within a subspace:

Section A ---> Section B (Parent: A)

Then, if a user has PermissionModerateContent on section A, they will have PermissionModerateContent on section B as well (permissions of section A are inherited within section B).

Please let me know what you think about this. If there's nothing against this feature I will take care of writing an ADR with better details. @bragaz @dadamu

[leobragaz]

I have no doubt this is a must have inside subspaces. I was thinking the same some time ago and ended up thinking about using groups for this but it actually doesn't make sense like that. With this, anyone can leverage their app with the desired level of complexity.

[dadamu]

Nice! I agree with it. Then, moderators can manage only one subspace instead of multiple subspaces.