Integrate transaction persistence into JpaTM (#717)

* Integrate transaction persistence into JpaTM

Store the serialized transaction whenever we commit from the JPA transaction
manager.  This change also adds:

-   The Transaction table.
-   The TransactionEntity which is stored in it.
-   Changes to the test infrastructure to register the TransactionEntity for
    tests where we don't load the nomulus schema.
-   A new configuration variable to allow us to turn the transaction
    persistence functionality on and off (default is "off").

* Changes for review.

* Incremented sequence number of flyway file

db/src/main/resources/sql/schema/nomulus.golden.sql

@@ -770,6 +770,35 @@ CREATE SEQUENCE public."SafeBrowsingThreat_id_seq"
 ALTER SEQUENCE public."SafeBrowsingThreat_id_seq" OWNED BY public."Spec11ThreatMatch".id;
 
 
+--
+-- Name: Transaction; Type: TABLE; Schema: public; Owner: -
+--
+
+CREATE TABLE public."Transaction" (
+    id bigint NOT NULL,
+    contents bytea
+);
+
+
+--
+-- Name: Transaction_id_seq; Type: SEQUENCE; Schema: public; Owner: -
+--
+
+CREATE SEQUENCE public."Transaction_id_seq"
+    START WITH 1
+    INCREMENT BY 1
+    NO MINVALUE
+    NO MAXVALUE
+    CACHE 1;
+
+
+--
+-- Name: Transaction_id_seq; Type: SEQUENCE OWNED BY; Schema: public; Owner: -
+--
+
+ALTER SEQUENCE public."Transaction_id_seq" OWNED BY public."Transaction".id;
+
+
 --
 -- Name: BillingCancellation billing_cancellation_id; Type: DEFAULT; Schema: public; Owner: -
 --
@@ -833,6 +862,13 @@ ALTER TABLE ONLY public."ReservedList" ALTER COLUMN revision_id SET DEFAULT next
 ALTER TABLE ONLY public."Spec11ThreatMatch" ALTER COLUMN id SET DEFAULT nextval('public."SafeBrowsingThreat_id_seq"'::regclass);
 
 
+--
+-- Name: Transaction id; Type: DEFAULT; Schema: public; Owner: -
+--
+
+ALTER TABLE ONLY public."Transaction" ALTER COLUMN id SET DEFAULT nextval('public."Transaction_id_seq"'::regclass);
+
+
 --
 -- Name: BillingCancellation BillingCancellation_pkey; Type: CONSTRAINT; Schema: public; Owner: -
 --
@@ -1001,6 +1037,14 @@ ALTER TABLE ONLY public."Spec11ThreatMatch"
     ADD CONSTRAINT "SafeBrowsingThreat_pkey" PRIMARY KEY (id);
 
 
+--
+-- Name: Transaction Transaction_pkey; Type: CONSTRAINT; Schema: public; Owner: -
+--
+
+ALTER TABLE ONLY public."Transaction"
+    ADD CONSTRAINT "Transaction_pkey" PRIMARY KEY (id);
+
+
 --
 -- Name: RegistryLock idx_registry_lock_repo_id_revision_id; Type: CONSTRAINT; Schema: public; Owner: -
 --