Server POW should work now

app/src/main/assets/db/migration/V1.2__Create_table_message.sql

@@ -8,6 +8,7 @@ CREATE TABLE Message (
   sent                    INTEGER,
   received                INTEGER,
   status                  VARCHAR(20)   NOT NULL,
+  initial_hash            BINARY(64)    UNIQUE,
 
   FOREIGN KEY (sender)    REFERENCES Address (address),
   FOREIGN KEY (recipient) REFERENCES Address (address)

app/src/main/assets/db/migration/V2.0__Update_table_message.sql

@@ -0,0 +1,7 @@
+-- This is done in V1.2, as SQLite doesn't support ADD CONSTRAINT and a proper migration
+-- wasn't really necessary yet.
+--
+-- This file is here to reduce confusion regarding to the original migration files.
+
+--ALTER TABLE Message ADD COLUMN initial_hash BINARY(64);
+--ALTER TABLE Message ADD CONSTRAINT initial_hash_unique UNIQUE(initial_hash);

app/src/main/assets/db/migration/V2.1__Create_table_POW.sql

@@ -0,0 +1,7 @@
+CREATE TABLE POW (
+  initial_hash          BINARY(64)    PRIMARY KEY,
+  data                  BLOB          NOT NULL,
+  version               BIGINT        NOT NULL,
+  nonce_trials_per_byte BIGINT        NOT NULL,
+  extra_bytes           BIGINT        NOT NULL
+);