Be stricter about JSON that is accepted by Synapse (#8106)

changelog.d/8106.bugfix

synapse/api/errors.py

synapse/federation/federation_server.py

synapse/federation/sender/transaction_manager.py

synapse/handlers/e2e_keys.py

synapse/handlers/identity.py

synapse/handlers/message.py

synapse/handlers/oidc_handler.py

synapse/handlers/ui_auth/checkers.py

synapse/http/client.py

synapse/http/federation/well_known_resolver.py

synapse/http/servlet.py

synapse/logging/opentracing.py

synapse/replication/tcp/commands.py

synapse/rest/client/v1/room.py

synapse/rest/client/v2_alpha/sync.py

synapse/rest/key/v2/remote_key_resource.py

synapse/storage/_base.py

synapse/storage/databases/main/events_worker.py

synapse/util/__init__.py