docker (compose): test environment variable + network alias: `SAT_TEST_ENV_E2E` is set to `1` to indicate that e2e environment requirement are available (notably specific accounts and hosts created). The e2e tests needing it won't be launched if this variable is not set. A network alias is set for the backend at `sat.test` (to have a tld available, needed for some network libraries like OpenSSL).

[component file_sharing]
tls_certificate = /usr/share/sat/certificates/server1.test.pem
tls_private_key = /usr/share/sat/certificates/server1.test-key.pem
http_upload_public_facing_url = https://sat.test:8888