BBJ – No one uses glue to install the cedar lining. If you cannot friction fit the wood (with miter cuts) then use brad nails in the center of the boards.
Moisture expansion and contraction in wood is a MAJOR concern when building wooded items with fitted parts. So put the boards in as a compression fit, or let a few brads hold them in a way that allows the wood to move. Remember that the kiln dried cedar is around 7-10% moisture content. When you season the humidor the wood will live at 70%.
Cedar wood movement 101- For Western Red Cedar (closest I could find)
Radial Shrinkage 2.4%
Tangential Shrinkage 5.0%
Tangential/ Radial 2.1%
Axial Shrinkage – Near zero.
If you have flat sawn cedar board 6” wide, the width can grow by more than ¼” from wet to dry. So on flat panels; use a ships lap joint with plenty of expansion space. The wood will see no size change along its length (length as the tree grows tall – true of most all woods). This is why desk top humidors have the boards mitered in, with the length horizontal, so the height can expand and contract.
Good luck with the humidor.