* use base64url encoding for public key in connection requests; only allow accepting invitations that were not accepted
* subscribe ContactConnection, fix test to use base64url encoding in key example
* asynchronous message sending to allow accepting messages when agent (or server) is offline
* send pending messages after agent restart; test for pending messages delivery when server restarted
* test pending message delivery after agent restart
* message delivery process per server
* test layout
* agent lock to avoid running subscriber and client processing in parallel; remove check that the connection is active when delivering a message
* use agent lock in agent functions
* commands to support introduction
* agent messages / envelopes to support introductions
* introductions and invitations table; insert record with random unique ID
* store class methods and types for introductions
* process INTRO and ACPT commands for connection introductions
* fix tests: add MonadFail constraint, remove OK response to JOIN
* process agent messages for introductions
* ICON notification when introduction is completed
* replace multiway if with case
* correction
* support random connection IDs
* save additional connection fields, refactor create connection funcs
* refactor
* refactor
* test duplex connection with random IDs
* store methods for introductions
* test introduction
* fix parsing of CON agent message
* test introduction with random connection IDs
* broadcast with random connection and broadcast IDs
* clean up sql
* database migrations
* fix: reverse order of down migrations
* use positional parameters in queries
* simplify migrations
* typo
* rename SchemaMigration to Migration
* move store initialization to IO monad
* agent: send CON to user when the 1st party responds HELLO; fix REPLY vulnerability
* test for getRcvConn
* add commented OK response to JOIN command
* store: use Only newtype to select one field
* sign and verify agent messages with key sent in HELLO (TODO: hardcoded block size - should use size from handshake; verify signature of HELLO message itself; possibly, different MSG status if signature was not verified (currently ignored) or failed to verify (currently fails with AGENT A_ENCRYPTION - alternatively, change it to AGENT A_SIGNATURE))
* remove hardcoded block size, make it 4096 bytes
* verify signature of HELLO message before it is added to RcvQueue
* refactor
* update doc
* rename functions
* inventory of error handling problems and types
* Change SMP protocol errors syntax
* connection errors in agent protocol (ERR CONN), STORE error -> AGENT error
* include exception in SEInternal error
* add MESSAGE errors, remove CRYPTO and SIZE errors
* agent protocol SYNTAX and AGENT errors
* BROKER errors
* group all client command (and agent response) errors
* BROKER TRANSPORT error
* simplify Client
* clean up
* transport errors
* simplify client
* parse / serialize agent errors
* differentiate crypto errors
* update errors.md
* make agent and SMP protocol errors consistent, simplify
* update doc
* test: parse / serialize protocol errors with QuickCheck
* add String to internal error
* exponential back-off when retrying to send HELLO
* refactor Client.hs
* replace fold with recursion in startTCPClient
* fail test if server did not start, refactor
* test: wait till TCP server stops
* test: refactor waiting for server to stop
* test: fail with error if server did not start/stop
* use separate db connections for each TCP client connection
* refactor atomically, increast delay in tests
* increase test delay for SMP server to start
* increase SMP ping frequency
* remove comment
* separate SQLite connection per thread, to support multi-threaded mode
* remove redundant import
