add graceful shutdown for sessions

[SamDanielThangarajan]

When connections are closed, the graceful_shutdown enables the sessions to drain all the messages read so far before the on_close core is invoked.

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
nasdaq_protocols
__init__.py	0	0	100%
nasdaq_protocols/asn1_app
__init__.py	9	0	100%
codegen.py	71	0	100%
core.py	55	4	92%	32–34, 75
soup_session.py	60	1	98%	28
nasdaq_protocols/asn1_app/templates
__init__.py	0	0	100%
nasdaq_protocols/common
__init__.py	6	0	100%
message_queue.py	102	0	100%
session.py	214	1	99%	258
sync_executor.py	50	3	94%	28–29, 88
types.py	36	4	88%	21, 27, 33, 37
utils.py	56	4	92%	21, 26, 80, 82
nasdaq_protocols/common/message
__init__.py	4	0	100%
codegen.py	48	0	100%
parser.py	149	6	95%	71, 74, 78, 85, 97–98
structures.py	216	9	95%	98, 248, 269–271, 278, 298, 302, 306
types.py	150	0	100%
nasdaq_protocols/common/message/templates
__init__.py	0	0	100%
nasdaq_protocols/fix
__init__.py	10	0	100%
_reader.py	29	2	93%	22, 25
codegen.py	17	3	82%	30–32
core.py	354	4	98%	234, 361–362, 461
session.py	88	0	100%
types.py	85	0	100%
nasdaq_protocols/fix/parser
__init__.py	3	0	100%
definitions.py	75	3	96%	160–162
generator.py	51	0	100%
parser.py	82	0	100%
version_types.py	24	0	100%
nasdaq_protocols/fix/parser/templates
__init__.py	0	0	100%
nasdaq_protocols/itch
__init__.py	11	0	100%
codegen.py	16	0	100%
core.py	25	0	100%
session.py	55	1	98%	27
nasdaq_protocols/ouch
__init__.py	11	0	100%
codegen.py	14	0	100%
core.py	31	1	96%	27
session.py	56	1	98%	27
nasdaq_protocols/soup
__init__.py	28	2	92%	126, 133
_reader.py	19	0	100%
core.py	142	0	100%
session.py	170	17	90%	62, 122–123, 188, 284–285, 295, 316–319, 332, 342–346
tools_soupapp_tail.py	18	0	100%
nasdaq_protocols/sqf
__init__.py	10	1	90%	64
codegen.py	14	0	100%
core.py	32	2	93%	25, 39
session.py	57	3	94%	27, 59, 91
TOTAL	2753	72	97%

Tests	Skipped	Failures	Errors	Time
369	5 💤	0 ❌	0 🔥	43.174s ⏱️