Fix cannot find control char when text length exceeds MAX_MENTION_QUERY_LENGTH

[krayc425]

• TL;DR: if text.length > MAX_MENTION_QUERY_LENGTH, the mentions will not working if the MAX_MENTION_QUERY_LENGTH's char in original text is already attributed.

• In HKWMentionsPluginV2, when controlCharactersToPrepend is set, it'll trim the parentTextView's text to be a substring of last MAX_MENTION_QUERY_LENGTH chars when trying to find the last unattributed control char. However, the location is offset-ed (offset = originalText.length - MAX_MENTION_QUERY_LENGTH) when passed to mentionAttributeAtLocation to determine whether the char at location in original text is already attributed. Before this fix, the location's value range is [0, trimmedText.length] while it should be [offset, trimmedText.length + offset]. Thus we need to add back the offset if the string is trimmed.

• Example:

1. Original text: <-- 200 chars, all attributed -->
2. When adding a control char: <-- 200 chars, all attributed --> @
3. Trimmed text: <-- 99 chars, all attributed --> @
4. Use the trimmed text to find the last unattributed control char in original string:

   <----- 200 chars, all attributed -----> @
   <--- 99 chars ---> @                            <- before fix
                 ⬆️
   <       offset      ><--- 99 chars ---> @       <- after fix
                                      ⬆️

   Now it will think the last control char is attributed, but actually it's not.

Before	After

[krayc425]

should we lix this change?

Added a config property enableControlCharacterMaxLengthFix, default to YES. Will add a kill switch when integrating w/voyager.

[krayc425]

/rerun-check "linkedin.Hakawai"