router: space endpoints

[avdb13]

Let's prioritize this next as we wanna have spaces as the fundamental building block of communities.

Space	route	commune-server	commune-rs
Join Space	POST /space/{space}/join	✅	❌
Leave Space	POST /space/{space}/leave	✅	❌
Create Space	POST /space/create	✅	❌
Create Space Room	POST /space/room/create	✅	❌
Get Space Custom Emoji	GET /space/emoji	✅	❌
Fetch Space Events	GET /{space}/events	✅	❌
Fetch Space Room Events	GET /{space}/{room_id}/events	✅	❌
Fetch Space State	GET /{space}/state	✅	❌
Fetch Space Power Levels	GET /{space}/power_levels	✅	❌