config UPDATE add support for TLS

New API for configuring TLS added. For the server, only it's certificate
is currently supported. For the client, only it's end-entity and
certificate-authority certificates are supported (as compared to
ietf-netconf-server module).

Each source and header files' includes were refactored (added
missing/deleted redundant).

New file to generate documentation from added to replace the old one.

New API parameters position changed. Split the API to SSH/TLS/common
files and added new common header for these.

Made changes to some internal structures and renamed some members.
diff --git a/tests/test_tls.c b/tests/test_tls.c
new file mode 100644
index 0000000..6693016
--- /dev/null
+++ b/tests/test_tls.c
@@ -0,0 +1,207 @@
+/**
+ * @file test_tls.c
+ * @author Roman Janota <janota@cesnet.cz>
+ * @brief libnetconf2 TLS authentication test
+ *
+ * @copyright
+ * Copyright (c) 2023 CESNET, z.s.p.o.
+ *
+ * This source code is licensed under BSD 3-Clause License (the "License").
+ * You may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://opensource.org/licenses/BSD-3-Clause
+ */
+
+#define _GNU_SOURCE
+
+#include <pthread.h>
+#include <setjmp.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <cmocka.h>
+
+#include "tests/config.h"
+
+#define NC_ACCEPT_TIMEOUT 2000
+#define NC_PS_POLL_TIMEOUT 2000
+
+struct ly_ctx *ctx;
+
+struct test_state {
+    pthread_barrier_t barrier;
+};
+
+static void *
+server_thread(void *arg)
+{
+    int ret;
+    NC_MSG_TYPE msgtype;
+    struct nc_session *session;
+    struct nc_pollsession *ps;
+    struct test_state *state = arg;
+
+    (void) arg;
+
+    ps = nc_ps_new();
+    assert_non_null(ps);
+
+    /* accept a session and add it to the poll session structure */
+    pthread_barrier_wait(&state->barrier);
+    msgtype = nc_accept(NC_ACCEPT_TIMEOUT, ctx, &session);
+    assert_int_equal(msgtype, NC_MSG_HELLO);
+
+    ret = nc_ps_add_session(ps, session);
+    assert_int_equal(ret, 0);
+
+    do {
+        ret = nc_ps_poll(ps, NC_PS_POLL_TIMEOUT, NULL);
+        assert_int_equal(ret & NC_PSPOLL_RPC, NC_PSPOLL_RPC);
+    } while (!(ret & NC_PSPOLL_SESSION_TERM));
+
+    nc_ps_clear(ps, 1, NULL);
+    nc_ps_free(ps);
+    nc_thread_destroy();
+    return NULL;
+}
+
+static void *
+client_thread(void *arg)
+{
+    int ret;
+    struct nc_session *session = NULL;
+    struct test_state *state = arg;
+
+    ret = nc_client_set_schema_searchpath(MODULES_DIR);
+    assert_int_equal(ret, 0);
+
+    /* set client cert */
+    ret = nc_client_tls_set_cert_key_paths(TESTS_DIR "/data/client.crt", TESTS_DIR "/data/client.key");
+    assert_int_equal(ret, 0);
+
+    /* set client ca */
+    ret = nc_client_tls_set_trusted_ca_paths(NULL, TESTS_DIR "/data");
+    assert_int_equal(ret, 0);
+
+    pthread_barrier_wait(&state->barrier);
+    session = nc_connect_tls("127.0.0.1", 10005, NULL);
+    assert_non_null(session);
+
+    nc_session_free(session, NULL);
+    nc_thread_destroy();
+    return NULL;
+}
+
+static void
+test_nc_tls(void **state)
+{
+    int ret, i;
+    pthread_t tids[2];
+
+    assert_non_null(state);
+
+    ret = pthread_create(&tids[0], NULL, client_thread, *state);
+    assert_int_equal(ret, 0);
+    ret = pthread_create(&tids[1], NULL, server_thread, *state);
+    assert_int_equal(ret, 0);
+
+    for (i = 0; i < 2; i++) {
+        pthread_join(tids[i], NULL);
+    }
+}
+
+static int
+setup_f(void **state)
+{
+    int ret;
+    struct lyd_node *tree = NULL;
+    struct test_state *test_state;
+
+    nc_verbosity(NC_VERB_VERBOSE);
+
+    /* init barrier */
+    test_state = malloc(sizeof *test_state);
+    assert_non_null(test_state);
+
+    ret = pthread_barrier_init(&test_state->barrier, NULL, 2);
+    assert_int_equal(ret, 0);
+
+    *state = test_state;
+
+    ret = ly_ctx_new(MODULES_DIR, 0, &ctx);
+    assert_int_equal(ret, 0);
+
+    ret = nc_server_init_ctx(&ctx);
+    assert_int_equal(ret, 0);
+
+    ret = nc_server_config_load_modules(&ctx);
+    assert_int_equal(ret, 0);
+
+    /* create new address and port data */
+    ret = nc_server_config_new_address_port(ctx, "endpt", NC_TI_OPENSSL, "127.0.0.1", "10005", &tree);
+    assert_int_equal(ret, 0);
+
+    /* create new server certificate data */
+    ret = nc_server_config_new_tls_server_certificate(ctx, "endpt", NULL, TESTS_DIR "/data/server.key", TESTS_DIR "/data/server.crt", &tree);
+    assert_int_equal(ret, 0);
+
+    /* create new end entity client cert data */
+    ret = nc_server_config_new_tls_client_certificate(ctx, "endpt", "client_cert", TESTS_DIR "/data/client.crt", &tree);
+    assert_int_equal(ret, 0);
+
+    /* create new client ca data */
+    ret = nc_server_config_new_tls_client_ca(ctx, "endpt", "client_ca", TESTS_DIR "/data/serverca.pem", &tree);
+    assert_int_equal(ret, 0);
+
+    ret = nc_server_config_new_tls_ctn(ctx, "endpt", 1,
+            "04:85:6B:75:D1:1A:86:E0:D8:FE:5B:BD:72:F5:73:1D:07:EA:32:BF:09:11:21:6A:6E:23:78:8E:B6:D5:73:C3:2D",
+            NC_TLS_CTN_SPECIFIED, "client", &tree);
+    assert_int_equal(ret, 0);
+
+    /* configure the server based on the data */
+    ret = nc_server_config_setup_diff(tree);
+    assert_int_equal(ret, 0);
+
+    /* initialize client */
+    nc_client_init();
+
+    ret = nc_server_init();
+    assert_int_equal(ret, 0);
+
+    lyd_free_all(tree);
+
+    return 0;
+}
+
+static int
+teardown_f(void **state)
+{
+    int ret = 0;
+    struct test_state *test_state;
+
+    assert_non_null(state);
+    test_state = *state;
+
+    ret = pthread_barrier_destroy(&test_state->barrier);
+    assert_int_equal(ret, 0);
+
+    free(*state);
+    nc_client_destroy();
+    nc_server_destroy();
+    ly_ctx_destroy(ctx);
+
+    return 0;
+}
+
+int
+main(void)
+{
+    const struct CMUnitTest tests[] = {
+        cmocka_unit_test_setup_teardown(test_nc_tls, setup_f, teardown_f),
+    };
+
+    setenv("CMOCKA_TEST_ABORT", "1", 1);
+    return cmocka_run_group_tests(tests, NULL, NULL);
+}