add a couple post endpoints + /timelines/home

internal/database/migrations/1693961486_follows.sql

@@ -0,0 +1,12 @@
+-- 2023-09-06: Account->blog follows
+
+-- +migrate Up
+
+create table account_follows (
+    account_id text not null references accounts (id) on delete cascade,
+    blog_id text not null references blogs (id) on delete cascade
+);
+
+-- +migrate Down
+
+drop table account_follows;

internal/database/migrations/1693999214_post_improvements.sql

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+-- 2023-09-06: Some improvements to posts
+
+-- +migrate Up
+
+alter table config add column post_character_limit integer not null default 5000;
+create index posts_blog_id_idx on posts (blog_id);
+
+create table post_recipients (
+    post_id    TEXT NOT NULL REFERENCES posts (id) ON DELETE CASCADE,
+    blog_id    TEXT NOT NULL REFERENCES blogs (id) ON DELETE CASCADE,
+
+    PRIMARY KEY (post_id, blog_id)
+);
+
+-- +migrate Down
+
+drop table post_recipients;
+drop index posts_blog_id_idx;
+alter table config drop column post_character_limit;