openapi: Move frequently used data to schemas section without any edits.
openapi: Move frequently used data to schemas section without any edits.

To increase code reusability and reduce code redundancy, we move data
structures which occur multiple times in the OpenAPI documentation to
the `schemas` section. Note that this a pure data movement commit
without any changes to the data beyond removing over-specific
descriptions (E.g. that suggest the user group was just created).

(Future commits will use these)

showell/zulip,brainwane/zulip,kou/zulip,showell/zulip,andersk/zulip,eeshangarg/zulip,zulip/zulip,punchagan/zulip,kou/zulip,showell/zulip,punchagan/zulip,kou/zulip,punchagan/zulip,hackerkid/zulip,hackerkid/zulip,zulip/zulip,kou/zulip,hackerkid/zulip,punchagan/zulip,zulip/zulip,hackerkid/zulip,punchagan/zulip,zulip/zulip,showell/zulip,brainwane/zulip,andersk/zulip,zulip/zulip,eeshangarg/zulip,brainwane/zulip,rht/zulip,kou/zulip,andersk/zulip,hackerkid/zulip,rht/zulip,rht/zulip,brainwane/zulip,andersk/zulip,kou/zulip,zulip/zulip,andersk/zulip,eeshangarg/zulip,zulip/zulip,eeshangarg/zulip,showell/zulip,punchagan/zulip,hackerkid/zulip,punchagan/zulip,rht/zulip,eeshangarg/zulip,brainwane/zulip,showell/zulip,rht/zulip,eeshangarg/zulip,kou/zulip,rht/zulip,rht/zulip,hackerkid/zulip,andersk/zulip,showell/zulip,brainwane/zulip,eeshangarg/zulip,brainwane/zulip,andersk/zulip