Remove Electrum support (#1750)

Electrum support was provided for mobile wallets, server nodes should always
run a bitcoind node as this provides more control (especially for utxo
management for anchor outputs channels).

Since wallets will use /~https://github.com/acinq/eclair-kmp instead of eclair,
we can now remove Electrum and API fee providers from eclair.

We also removed 3rd-party fee API providers that were only used on wallets.

eclair-core/src/main/resources/reference.conf

@@ -20,7 +20,6 @@ eclair {
   // override this with a script/exe that will be called everytime a new database backup has been created
   # backup-notify-script = "/absolute/path/to/script.sh"
 
-  watcher-type = "bitcoind" // other *experimental* values include "electrum"
   watch-spent-window = 1 minute // at startup watches will be put back within that window to reduce herd effect; must be > 0s
 
   bitcoind {
@@ -91,7 +90,6 @@ eclair {
   on-chain-fees {
     min-feerate = 1 // minimum feerate in satoshis per byte
     smoothing-window = 6 // 1 = no smoothing
-    provider-timeout = 5 seconds // max time we'll wait for answers from a fee provider before we fallback to the next one
 
     default-feerates { // those are per target block, in satoshis per kilobyte
       1 = 210000

eclair-core/src/main/scala/fr/acinq/eclair/NodeParams.scala

@@ -19,7 +19,6 @@ package fr.acinq.eclair
 import com.typesafe.config.{Config, ConfigFactory, ConfigValueType}
 import fr.acinq.bitcoin.Crypto.PublicKey
 import fr.acinq.bitcoin.{Block, ByteVector32, Crypto, Satoshi}
-import fr.acinq.eclair.NodeParams.WatcherType
 import fr.acinq.eclair.Setup.Seeds
 import fr.acinq.eclair.blockchain.fee._
 import fr.acinq.eclair.channel.Channel
@@ -79,7 +78,6 @@ case class NodeParams(nodeKeyManager: NodeKeyManager,
                       maxReconnectInterval: FiniteDuration,
                       chainHash: ByteVector32,
                       channelFlags: Byte,
-                      watcherType: WatcherType,
                       watchSpentWindow: FiniteDuration,
                       paymentRequestExpiry: FiniteDuration,
                       multiPartPaymentExpiry: FiniteDuration,
@@ -110,11 +108,10 @@ case class NodeParams(nodeKeyManager: NodeKeyManager,
 
 object NodeParams extends Logging {
 
+  // @formatter:off
   sealed trait WatcherType
-
   object BITCOIND extends WatcherType
-
-  object ELECTRUM extends WatcherType
+  // @formatter:on
 
   /**
    * Order of precedence for the configuration parameters:
@@ -123,7 +120,7 @@ object NodeParams extends Logging {
    * 3) Optionally provided config
    * 4) Default values in reference.conf
    */
-  def loadConfiguration(datadir: File) =
+  def loadConfiguration(datadir: File): Config =
     ConfigFactory.parseProperties(System.getProperties)
       .withFallback(ConfigFactory.parseFile(new File(datadir, "eclair.conf")))
       .withFallback(ConfigFactory.load())
@@ -214,11 +211,6 @@ object NodeParams extends Logging {
     val color = ByteVector.fromValidHex(config.getString("node-color"))
     require(color.size == 3, "color should be a 3-bytes hex buffer")
 
-    val watcherType = config.getString("watcher-type") match {
-      case "electrum" => ELECTRUM
-      case _ => BITCOIND
-    }
-
     val watchSpentWindow = FiniteDuration(config.getDuration("watch-spent-window").getSeconds, TimeUnit.SECONDS)
     require(watchSpentWindow > 0.seconds, "watch-spent-window must be strictly greater than 0")
 
@@ -364,7 +356,6 @@ object NodeParams extends Logging {
       maxReconnectInterval = FiniteDuration(config.getDuration("max-reconnect-interval").getSeconds, TimeUnit.SECONDS),
       chainHash = chainHash,
       channelFlags = config.getInt("channel-flags").toByte,
-      watcherType = watcherType,
       watchSpentWindow = watchSpentWindow,
       paymentRequestExpiry = FiniteDuration(config.getDuration("payment-request-expiry").getSeconds, TimeUnit.SECONDS),
       multiPartPaymentExpiry = FiniteDuration(config.getDuration("multi-part-payment-expiry").getSeconds, TimeUnit.SECONDS),