Limit Sesh's mentionable roles
**Define what roles are pingable in server settings and/or channel overrides.** (Ignore non-admin event creator discord permissions) There are cases where I want Sesh to be able to mention all roles, but not allow normal members to mention these roles. **Explanation** **Already possible with current setup:** 1. Admin can use sesh to mention all roles no matter what. 2. Sesh can be given permission to ping all roles. 3. Using discord permissions, non-admin members can only ping certain roles (which extends to Sesh). **New behavior** Sesh __*ignores*__ mentions permissions on individual roles and from individual non-admin users. Server or channel override settings will specify that Non-admin members are only able to ping roles A, B, and C from the sesh dashboard. **Longer Explanation** In my server, there are several roles with differing pinging permissions. Members don't have the ability to ping _all_ roles, but they _do_ have the ability to ping roles that Sesh should not ping. Let's say that a member has discord permissions to ping roles A, B, C, and D. (Sesh has the permission to ping all roles.) But I want Sesh to only allow members to ping role B for events, despite what the discord permissions say. Alternatively: Let us say that a member only has the discord permission to ping role A. But the server's default event ping list role is role B. I would still like Sesh to let that member ping role B for events.