[IMP] fields: allow shared fields

Given the following variables:
    * Module A
    * Module B
    * Model M
    * Field X of model M

If module A defines M.X and is installed, an xmlid for this field is
generated in the form of A.field_M_X

Before this commit:

If module B defines M.X as well and is installed after module A, no
xmlid is generated.

This means that if module A is uninstalled, the single xmlid pointing to
M.X will be deleted and thus, the field itself will be deleted as well,
therefore any views from module B referencing M.X will crash.

After this commit:

If module B (or any subsequent modules) define M.X, an xmlid will be
generated in the form of B.field_M_X.

If module A is uninstalled, the xmlid A.field_M_X will be deleted, but
B.field_M_X will remain and thus the field itself won't be deleted.

This system means that for a single actual field, there can be multiple
xmlids, each xmlid sharing the same field, thus the name "shared
fields".

Task ID 38016

0 files changed, 0 insertions, 0 deletions