[1.7.x] Fixed #24054 -- Enabled sqlsequencereset for apps with migrations.

Backport of c2e419c26781b88f2b34b445f450b735267155b0 from master
[1.7.x] Clarified custom header instructions in tutorial 2.

Backport of 0821b3d53ccd575de92ed679d173d779e1ad5acd from master