v0.1.0-alpha.2

The second alpha, for the same two Heltec WiFi LoRa 32 V3 boards and as many more as you have. It
is what the first one lacked to get past two boards on a desk without a serial terminal.

It is an alpha. The protocol is a draft and will change, and a later build may not talk to this
one or keep its sessions. Nobody outside the project has reviewed the cryptography. Do not rely
on it for anything that matters.

What changed

• A new board is let in from the web client. A board accepts first contact from any address
  saved as a contact. When it refuses one for not being a contact, the client says who asked and
  offers to save it; that board is taken the next time it tries. A board that already holds
  eight sessions refuses for want of room instead, and the client says so: end a session first.
  accept on the console still works.
• A session can be ended from the web client. The board forgets its keys for that node and
  gives up the messages still waiting for it. The other board is not told: its messages go
  unanswered until the board that ended it sends a message, or the other ends its session too.
• The web client sets power, region and role. The board restarts to apply one, and the page
  connects again.
• The companion protocol is version 1: END_SESSION and ASKED are new. A client of version 0
  works as before.

Updating

A board running 0.1.0-alpha.1 keeps its address, sessions and contacts if you write the
-app.bin image at 0x10000; https://ternmesh.org/flash does that when you say the board runs
Tern already.
This build talks to 0.1.0-alpha.1 on the air.

tern-heltec-v3-us915-0.1.0-alpha.2.bin	United States, Canada: 921.25 MHz
tern-heltec-v3-eu868-0.1.0-alpha.2.bin	Europe: 869.475 MHz, at most 10% of any hour

The full images are written at 0x0, replace whatever is on the board, and give it a new
address. Never power a board with nothing on the antenna connector. SHA256SUMS has the
SHA-256 of each image.

What is still not in it

• First contact does not follow routes. Two boards must hear each other directly to meet.
  Once they have, messages between them may go through relays.
• No group or broadcast messages. Every message is to one address.
• Messages are kept only in memory on the board. The web client keeps what it has seen in
  the browser; a message that arrives while no client is connected is lost if the board restarts
  before one connects.
• The web client does not use Bluetooth yet, so there is no phone client.
• Boards start at 2 dBm, a bench setting that reaches across a building, not a town, until
  you raise it.
• Keys sit in flash unencrypted. Anyone holding the board can read them.
• One board only. An nRF52 port is next.