Manila Administrators create share group types with shared_file_systems_share_types and group-specs to allow users to request a group type of share group to create. The Administrator chooses a name for the share group type and decides how to communicate the significance of the different share group types in terms that the users should understand or need to know. By design, most of the details of a share group type (the extra-specs) are not exposed to users -- only Administrators.
Refer to the manila client command-line help for information on how to create a share group type and set "share types", "group-spec" key/value pairs for a share group type.
The group specs contains the group capabilities, similar to snapshot_support in share types. Users know what a group can do from group specs.
The group specs is an exact match requirement in share group filter (such as ConsistentSnapshotFilter). When the ConsistentSnapshotFilter is enabled (it is enabled by default), the scheduler will only create a share group on a backend that reports capabilities that match the share group type's group-spec keys.
For group capabilities that apply to multiple backends a common capability can be created. Like all other backend reported group capabilities, these group capabilities can be used verbatim as group_specs in share group types used to create share groups.