System to create internal redirects within each book

Created by: seanmadsen

Within the Developer Guide content migration, a need emerged rather quickly to be able to move a page without giving a 404 error to any incoming links. The docs system should provide a way for each book to specify internal redirects.

MkDocs has stated that they want redirection to happen at the server level, so it seems our docs system should be responsible for providing this feature.

For comparison, Read The Docs offers this feature. Though, as someone who has never used RTD, reading their description of this feature still leaves me somewhat confused as to the process that content editors must follow to create such redirects.