Add "pending migrations" status to docs

Author: jeremystretch

docs/models/branch.md

@@ -20,17 +20,18 @@ The unique, randomly-generated identifier of the PostgreSQL schema which houses
 
 The current status of the branch. This must be one of the following values.
 
-| Status       | Description                                                       |
-|--------------|-------------------------------------------------------------------|
-| New          | Not yet provisioned in the database                               |
-| Provisioning | A job is running to provision the branch's PostgreSQL schema      |
-| Ready        | The branch is healthy and ready to be synchronized or merged      |
-| Syncing      | A job is running to synchronize changes from main into the branch |
-| Merging      | A job is running to merge changes from the branch into main       |
-| Reverting    | A job is running to revert previously merged changes in main      |
-| Merged       | Changes from this branch have been successfully merged into main  |
-| Archived     | A merged branch which has been deprovisioned in the database      |
-| Failed       | Provisioning the schema for this branch has failed                |
+| Status             | Description                                                                   |
+|--------------------|-------------------------------------------------------------------------------|
+| New                | Not yet provisioned in the database                                           |
+| Provisioning       | A job is running to provision the branch's PostgreSQL schema                  |
+| Ready              | The branch is healthy and ready to be synchronized or merged                  |
+| Syncing            | A job is running to synchronize changes from main into the branch             |
+| Merging            | A job is running to merge changes from the branch into main                   |
+| Reverting          | A job is running to revert previously merged changes in main                  |
+| Pending Migrations | One or more database migrations must be applied before the branch can be used |
+| Merged             | Changes from this branch have been successfully merged into main              |
+| Archived           | A merged branch which has been deprovisioned in the database                  |
+| Failed             | Provisioning the schema for this branch has failed                            |
 
 ### Last Sync