res_pjsip: add option to enable ContactStatus event when contact is updated

The commit I2f97ebfa79969a36a97bb7b9afd5b6268cf1a07d removed sending out
the ContactStatus AMI event when a contact is updated.
Thist change broke things which rely on old behavior.

This patch adds a new PJSIP global configuration option
'send_contact_status_on_update_registration' to be able to preserve old
ContactStatus behavior.
By default new behavior, i.e. the ContactStatus event will not be sent when a
device refreshes its registration.

Change-Id: I706adf7584e7077eb6bde6d9799ca408bc82ce46

contrib/ast-db-manage/config/versions/0838f8db6a61_pjsip_add_send_contact_status_on_update_.py

@@ -0,0 +1,39 @@
+"""pjsip add send_contact_status_on_update_registration
+
+Revision ID: 0838f8db6a61
+Revises: 1ac563b350a8
+Create Date: 2018-12-18 14:45:07.811415
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = '0838f8db6a61'
+down_revision = '1ac563b350a8'
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects.postgresql import ENUM
+
+AST_BOOL_NAME = 'ast_bool_values'
+# We'll just ignore the n/y and f/t abbreviations as Asterisk does not write
+# those aliases.
+AST_BOOL_VALUES = [ '0', '1',
+                    'off', 'on',
+                    'false', 'true',
+                    'no', 'yes' ]
+
+
+def upgrade():
+    ############################# Enums ##############################
+
+    # ast_bool_values has already been created, so use postgres enum object
+    # type to get around "already created" issue - works okay with mysql
+    ast_bool_values = ENUM(*AST_BOOL_VALUES, name=AST_BOOL_NAME, create_type=False)
+
+    op.add_column('ps_globals', sa.Column('send_contact_status_on_update_registration', ast_bool_values))
+
+
+def downgrade():
+    if op.get_context().bind.dialect.name == 'mssql':
+        op.drop_constraint('ck_ps_globals_send_contact_status_on_update_registration_ast_bool_values', 'ps_globals')
+    op.drop_column('ps_globals', 'send_contact_status_on_update_registration')