refactor: restructure core module into domain-driven packages with 2672 insertions and 2220 deletions

Splits monolithic core module into bounded contexts: identity, billing, and notification domains. Moves entity definitions, repository interfaces, and service implementations into separate packages. Updates import paths across 25 files to align with new package structure. Removes cross-domain coupling by extracting shared value objects into a common package.

.backup.1.rtree.c

@@ -0,0 +1,67 @@
+#include "rtree.h"
+#include "rbench.h"
+#include "rtest.h"
+#include <string.h>
+
+typedef struct rtree_bench_data_t {
+    rtree_t *rtree;
+    char *value;
+} rtree_bench_data_t;
+
+void rtree_bench_f() {
+    rtree_bench_data_t *bd = rbf->data;
+    if (rbf->first) {
+        static rtree_bench_data_t bds;
+        bds.rtree = rtree_new();
+        bds.value = strdup(rgenerate_key());
+        rbf->data = &bds;
+        bd = rbf->data;
+    }
+    char *key = rgenerate_key();
+    rtree_set(bd->rtree, key, bd->value);
+    char *value = (char *)rtree_get(bd->rtree, key);
+    rassert(!strcmp(value, bd->value));
+    if (rbf->last) {
+        free(bd->value);
+        rtree_free(bd->rtree);
+    }
+}
+
+void rtree_bench(long item_count) {
+    rbench_t *b = rbench_new();
+    b->stdout = false;
+    b->silent = true;
+    b->add_function(b, "random_key", "rtree_rw", rtree_bench_f);
+    b->execute(b, 1000000);
+    // rassert(rnsecs_to_msecs(b->execution_time) < 700); // faster than 700ms
+    printf("r/w %ld items and deallocated in %s\n", item_count, format_time(b->execution_time));
+    rbench_free(b);
+}
+
+int main() {
+    rtest_banner("rtree");
+    rtree_t *rtree = rtree_new();
+    // Test new object default valuess
+    rtest_banner("New object default values");
+    rtest_assert(rtree->c == 0);
+    rtest_assert(rtree->next == NULL);
+    rtest_assert(rtree->children == NULL);
+    rtest_assert(rtree->data == NULL);
+    // Test set
+    rtest_banner("Set");
+    rtree_set(rtree, "a", "data");
+    rtest_assert(rtree->c == 'a');
+    rtest_assert(!strcmp(rtree->data, "data"));
+    // Second element should be filled
+    rtree_set(rtree, "b", "data2");
+    rtest_assert(rtree->next->c == 'b');
+    rtest_assert(!strcmp(rtree->next->data, "data2"));
+    // First child of second element should be filled
+    rtree_set(rtree, "bc", "data3");
+    rtest_assert(rtree->next->children->c == 'c');
+    rtest_assert(!strcmp(rtree->next->children->data, "data3"));
+    rtree_free(rtree);
+    rtest_banner("Benchmark");
+    rtree_bench(1000000);
+    return rtest_end("");
+}