Use null for optional foreign keys

Author: jc21

backend/embed/migrations/mysql/20201013035318_initial_schema.sql

@@ -104,15 +104,15 @@ CREATE TABLE IF NOT EXISTS `dns_provider`
 	FOREIGN KEY (`user_id`) REFERENCES `user`(`id`) ON DELETE CASCADE
 );
 
-CREATE TABLE IF NOT EXISTS certificate
+CREATE TABLE IF NOT EXISTS `certificate`
 (
 	`id` INT AUTO_INCREMENT PRIMARY KEY,
 	`created_at` BIGINT NOT NULL DEFAULT 0,
 	`updated_at` BIGINT NOT NULL DEFAULT 0,
 	`is_deleted` INT NOT NULL DEFAULT 0, -- int on purpose, gormism
 	`user_id` INT NOT NULL,
 	`type` VARCHAR(50) NOT NULL, -- custom,dns,http
-	`certificate_authority_id` INT, -- 0 for a custom cert
+	`certificate_authority_id` INT, -- null for a custom cert
 	`dns_provider_id` INT, -- 0, for a http or custom cert
 	`name` VARCHAR(50) NOT NULL,
 	`domain_names` TEXT NOT NULL,
@@ -216,12 +216,12 @@ CREATE TABLE IF NOT EXISTS host
 	`nginx_template_id` INT NOT NULL,
 	`listen_interface` VARCHAR(50) NOT NULL DEFAULT '',
 	`domain_names` TEXT NOT NULL,
-	`upstream_id` INT NOT NULL DEFAULT 0,
+	`upstream_id` INT,
 	`proxy_scheme` VARCHAR(50) NOT NULL DEFAULT '',
 	`proxy_host` VARCHAR(50) NOT NULL DEFAULT '',
 	`proxy_port` INT NOT NULL DEFAULT 0,
-	`certificate_id` INT NOT NULL DEFAULT 0,
-	`access_list_id` INT NOT NULL DEFAULT 0,
+	`certificate_id` INT,
+	`access_list_id` INT,
 	`ssl_forced` BOOLEAN NOT NULL DEFAULT FALSE,
 	`caching_enabled` BOOLEAN NOT NULL DEFAULT FALSE,
 	`block_exploits` BOOLEAN NOT NULL DEFAULT FALSE,

backend/embed/migrations/postgres/20201013035318_initial_schema.sql

@@ -187,12 +187,12 @@ CREATE TABLE "host" (
 	"nginx_template_id" INTEGER NOT NULL REFERENCES "nginx_template"("id") ON DELETE CASCADE,
 	"listen_interface" TEXT NOT NULL DEFAULT '',
 	"domain_names" TEXT NOT NULL,
-	"upstream_id" INTEGER NOT NULL DEFAULT 0 REFERENCES "upstream"("id") ON DELETE CASCADE,
+	"upstream_id" INTEGER REFERENCES "upstream"("id") ON DELETE CASCADE,
 	"proxy_scheme" TEXT NOT NULL DEFAULT '',
 	"proxy_host" TEXT NOT NULL DEFAULT '',
 	"proxy_port" INTEGER NOT NULL DEFAULT 0,
-	"certificate_id" INTEGER NOT NULL DEFAULT 0 REFERENCES "certificate"("id") ON DELETE CASCADE,
-	"access_list_id" INTEGER NOT NULL DEFAULT 0 REFERENCES "access_list"("id") ON DELETE CASCADE,
+	"certificate_id" INTEGER REFERENCES "certificate"("id") ON DELETE CASCADE,
+	"access_list_id" INTEGER REFERENCES "access_list"("id") ON DELETE CASCADE,
 	"ssl_forced" BOOLEAN NOT NULL DEFAULT FALSE,
 	"caching_enabled" BOOLEAN NOT NULL DEFAULT FALSE,
 	"block_exploits" BOOLEAN NOT NULL DEFAULT FALSE,

backend/embed/migrations/sqlite/20201013035318_initial_schema.sql

@@ -216,12 +216,12 @@ CREATE TABLE IF NOT EXISTS `host`
 	nginx_template_id INTEGER NOT NULL,
 	listen_interface TEXT NOT NULL DEFAULT "",
 	domain_names TEXT NOT NULL,
-	upstream_id INTEGER NOT NULL DEFAULT 0,
+	upstream_id INTEGER,
 	proxy_scheme TEXT NOT NULL DEFAULT "",
 	proxy_host TEXT NOT NULL DEFAULT "",
 	proxy_port INTEGER NOT NULL DEFAULT 0,
-	certificate_id INTEGER NOT NULL DEFAULT 0,
-	access_list_id INTEGER NOT NULL DEFAULT 0,
+	certificate_id INTEGER,
+	access_list_id INTEGER,
 	ssl_forced INTEGER NOT NULL DEFAULT 0,
 	caching_enabled INTEGER NOT NULL DEFAULT 0,
 	block_exploits INTEGER NOT NULL DEFAULT 0,