feat(bot): add proxy error config (#544)

PluralKit.Core/Database/Functions/MessageContext.cs

@@ -29,4 +29,5 @@ public class MessageContext
     public bool AllowAutoproxy { get; }
     public int? LatchTimeout { get; }
     public bool CaseSensitiveProxyTags { get; }
+    public bool ProxyErrorMessageEnabled { get; }
 }

PluralKit.Core/Database/Functions/functions.sql

@@ -15,13 +15,14 @@ create function message_context(account_id bigint, guild_id bigint, channel_id b
         system_avatar text,
         allow_autoproxy bool,
         latch_timeout integer,
-        case_sensitive_proxy_tags bool
+        case_sensitive_proxy_tags bool,
+        proxy_error_message_enabled bool
     )
 as $$
     -- CTEs to query "static" (accessible only through args) data
     with
         system as (select systems.*, system_config.latch_timeout, system_guild.tag as guild_tag, system_guild.tag_enabled as tag_enabled, 
-                          allow_autoproxy as account_autoproxy, system_config.case_sensitive_proxy_tags from accounts
+                          allow_autoproxy as account_autoproxy, system_config.case_sensitive_proxy_tags, system_config.proxy_error_message_enabled from accounts
             left join systems on systems.id = accounts.system
             left join system_config on system_config.system = accounts.system
             left join system_guild on system_guild.system = accounts.system and system_guild.guild = guild_id
@@ -43,7 +44,8 @@ as $$
         system.avatar_url                          as system_avatar,
         system.account_autoproxy                   as allow_autoproxy,
         system.latch_timeout                       as latch_timeout,
-        system.case_sensitive_proxy_tags           as case_sensitive_proxy_tags
+        system.case_sensitive_proxy_tags           as case_sensitive_proxy_tags,
+        system.proxy_error_message_enabled         as proxy_error_message_enabled
     -- We need a "from" clause, so we just use some bogus data that's always present
     -- This ensure we always have exactly one row going forward, so we can left join afterwards and still get data
     from (select 1) as _placeholder