Fieldtype discovery wrong for strings starting with zero

[elektro-wolle]

Make sure that:

• You have read the contribution guidelines.
• You specify the logstash-gelf version and environment so it's obvious which version is affected
• You provide a reproducible test case (either descriptive of as JUnit test) if it's a bug or the expected behavior differs from the actual behavior.

The following test-cases will fail against logstash-gelf-1.14.1

    @Test
    void testString() {
        assertThat(ValueDiscovery.discover("deadbeef")).isEqualTo(ValueDiscovery.Result.STRING);
    }

    @Test
    void testStringWithLeadingZeroAndHex() {
        assertThat(ValueDiscovery.discover("0deadbeef")).isEqualTo(ValueDiscovery.Result.STRING);
    }

    @Test
    void testStringZeroAndP() {
        assertThat(ValueDiscovery.discover("0p")).isEqualTo(ValueDiscovery.Result.STRING);
    }

    @Test
    void testStringZeroAndX() {
        assertThat(ValueDiscovery.discover("0x")).isEqualTo(ValueDiscovery.Result.STRING);
    }

    @Test
    void testStringZeroXP() {
        assertThat(ValueDiscovery.discover("0xp")).isEqualTo(ValueDiscovery.Result.STRING);
    }

[mp911de]

Value type discovery was implemented on a best-effort basis without reimplementing a full parser. Type discovery allows for hex values and scientific notation inputs but may lead to wrong discovery results. Do you want to submit a pull request to address that issue?

[elektro-wolle]

I'm currently working on the PR.