Rather than have three methods which have to have the same interface,
factor out a separate interface which is provided by three implementations.

I find it easier to grok the code this way.

This is a first step to checking that the key is valid at the required moment.

The idea here is that, rather than passing VerifyKey objects in and out of the
storage layer, we instead pass FetchKeyResult objects, which simply wrap the
VerifyKey and add a valid_until_ts field.

* Pass time_added_ms into process_v2_response

* Simplify process_v2_response

We can merge old_verify_keys into verify_keys, and reduce the number of dicts
flying around.

These were never used, and poking arbitary data into objects from other
packages seems confusing at best.

Storing server keys hammered the database a bit. This replaces the
implementation which stored a single key, with one which can do many updates at
once.

I was staring at this function trying to figure out wtf it was actually
doing. This is (hopefully) a non-functional refactor which makes it a bit
clearer.

This reverts commit c31e375a.

requests 2.22.0 as been released supporting urllib3 1.25.2

Signed-off-by: Marcus Hoffmann <bubu@bubu1.eu>

* expose SlavedProfileStore to ClientReaderSlavedStore

Add missing backslash

Only count aggregations from distinct senders

Block attempts to annotate the same event twice

Implements https://github.com/matrix-org/matrix-doc/pull/2002.

When considering the candidates to be forward-extremities, we must exclude soft
failures.

Hopefully fixes #5090.

* Pin eliot to <1.8 on python 3.5.2

Fixes https://github.com/matrix-org/synapse/issues/5199

* Add support for 'markers' to python_dependencies

* tell xargs not to strip quotes

Add startup background job for account validity

If we remove support for a particular room version, we should behave more
gracefully. This should make client requests fail with a 400 rather than a 500,
and will ignore individiual PDUs in a federation transaction, rather than the
whole transaction.

This reverts commit ce5bcefc.

This caused:

```
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/local/lib/python3.7/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/home/synapse/src/synapse/app/client_reader.py", line 32, in <module>
    from synapse.replication.slave.storage import SlavedProfileStore
ImportError: cannot import name 'SlavedProfileStore' from 'synapse.replication.slave.storage' (/home/synapse/src/synapse/replication/slave/storage/__init__.py)
error starting synapse.app.client_reader('/home/synapse/config/workers/client_reader.yaml') (exit code: 1); see above for logs
```

Implements MSC1884

Rename relation types to match MSC