feat(entities) Adds build entity and sql schema

entity/BUILD.bazel

@@ -5,6 +5,7 @@ go_library(
     srcs = [
         "batch.go",
         "batch_dependent.go",
+        "build.go",
         "change_provider.go",
         "request.go",
     ],

entity/build.go

@@ -0,0 +1,34 @@
+package entity
+
+// BuildStatus defines the possible states of a build.
+type BuildStatus string
+
+const (
+	// BuildStateUnknown is the unreachable state. It is set by default when the structure is initialized. It should never be seen in the system.
+	BuildStateUnknown BuildStatus = ""
+	// TODO: Add comprehensive list of known build states.
+)
+
+// SpeculationPathInfo represents the base and head commits of a speculation path used in a build.
+type SpeculationPathInfo struct {
+	// Base is a list of batchIDs(in order) that form the base of this speculation path.
+	Base []string
+}
+
+// Build represents a build scheduled for a batch along a specific speculation path.
+// All fields except the Status are immutable after creation.
+type Build struct {
+	// ID represents the build ID. It is the responsibility of a build management system to ensure
+	// that this is unique.
+	ID string
+	// BatchID is the batch for which this build is scheduled.
+	BatchID string
+	// SpeculationPath is the speculation path that represents this build. For
+	// a given batch this path is crafted from the graph that is generated from the
+	// dependencies of this batch.
+	SpeculationPath SpeculationPathInfo
+	// Score represents the build prediction score for this speculation path.
+	Score float32
+	// Status represents the state of the build lifecycle this build is in.
+	Status BuildStatus
+}

extension/storage/mysql/schema/build.sql

@@ -0,0 +1,8 @@
+CREATE TABLE IF NOT EXISTS build (
+    id VARCHAR(255) NOT NULL,
+    batch_id VARCHAR(255) NOT NULL,
+    speculation_path JSON NOT NULL,
+    score FLOAT NOT NULL,
+    status VARCHAR(64) NOT NULL,
+    PRIMARY KEY (id)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;