chore: increase a number of Jetty threads to fix the integration tests

Correction for 08a07ce commit.

Previously, a number of threads was enough only for handling a single client connection. When we
tried to create a series with an image that should be downloaded from the same server, we couldn't
do that as an only worker was busy -- it was waiting when a server downloads an image from itself.

Fix #1633

src/main/resources/application-postgres.properties

@@ -39,8 +39,8 @@ logging.level.org.springframework.web.servlet.mvc.method.annotation.RequestMappi
 app.use-cdn: false
 
 # reduce a number of threads (8 and 200 by default)
-server.jetty.threads.min: 2
-server.jetty.threads.max: 4
+server.jetty.threads.min: 4
+server.jetty.threads.max: 6
 
 # Full list of autoconfiguration classes:
 # https://docs.spring.io/spring-boot/docs/2.3.x/reference/html/appendix-auto-configuration-classes.html

src/main/resources/application-test.properties

@@ -14,8 +14,8 @@ spring.h2.console.path: /console
 server.max-http-header-size: 4096
 
 # reduce a number of threads (8 and 200 by default)
-server.jetty.threads.min: 2
-server.jetty.threads.max: 4
+server.jetty.threads.min: 4
+server.jetty.threads.max: 6
 
 spring.messages.cache-duration: 1m
 spring.messages.fallback-to-system-locale: false

src/main/resources/application-travis.properties

@@ -38,8 +38,8 @@ app.preview.dir: /tmp/preview
 app.use-cdn: false
 
 # reduce a number of threads (8 and 200 by default)
-server.jetty.threads.min: 2
-server.jetty.threads.max: 4
+server.jetty.threads.min: 4
+server.jetty.threads.max: 6
 
 # Full list of autoconfiguration classes:
 # https://docs.spring.io/spring-boot/docs/2.3.x/reference/html/appendix-auto-configuration-classes.html